I have chosen to write about adaptive music because it is something I have often thought about myself while playing games or making music (as it happens, two of my favorite activities). I wondered why, even though it is technically possible (and has been for many years) and can really add a lot to a game, adaptive music is so rarely used in video games. I already read some articles about adaptive music so I could form my own educated guess about why it is so rarely found in games. Still, I was interested in reading more about adaptive music and decided that it would be the subject of this paper.
I was expecting to find a little more written material on adaptive audio, but it turned out it is quite hard to find good sources on the subject. In the end I had to make do with a number of articles and papers on adaptive music.
I also wanted to include some simple case studies, but unfortunately I didn't have the means to acquire and thoroughly play any games that have an adaptive soundtrack.
I'd like to thank Gamasutra.com for having a lot of informative articles on their website.
I also want to thank Evert Hoogendoorn for assisting me in writing this paper.
The game industry is usually referred to as a "young industry", and it is true that we probably have some exciting years of growth and development in front of us. Some fields, however, have been developing faster than others.
Computer graphics have been advancing in huge leaps over the past years, with each new generation of video cards adding new techniques and ways to make games look better or more realistic, and every new generation of consoles increasing the graphical power considerably (although the Nintendo Wii might be said to break this "tradition").
The field that has been left behind is audio. Although music and sound effects for games have gotten better in terms of audio quality (advancing from simple beeps to fully orchestrated scores), new techniques and ways of using music in games have not developed as quickly as they could (and perhaps should) have.
Recently, there is a lot of talk in the game industry about adaptive music (sometimes incorrectly referred to as interactive music). Adaptive music is the (long overdue) leap forward in the game audio field that we were waiting for, and I will try to describe its possibilities in this paper.
The questions I will try to answer are:
This paper is not about sound effects or ambient sounds, though I might mention them from time to time. I will focus only on music.
Some people talk about interactive music and some about adaptive music. Most of the time, they are talking about the same thing, especially when these terms are used in relation to music for video games. However, I think adaptive is a more suitable term in this regard (I will explain why after we look a little closer at what adaptive music is).
In soundtracks for movies, the music can support the action onscreen perfectly, because it is known from one second to the next what is going to happen. This allows a composer to write music that stimulates the viewers' emotions at exactly the right moments: A startling orchestra bang when a character is shocked by a sudden movement in a scary movie, violins that start playing exactly as two characters kiss, etc.
Movies are a 'linear' medium, and so a regular, linear soundtrack works perfectly for a movie. In video games, on the other hand, most of the time it is impossible to know in advance what will be happening on screen from one second to the next. You can never tell exactly how many seconds it will take a player to pass through a room, or when exactly the player will fire his gun and kill an enemy. Using a normal soundtrack means you can only try to catch the general feeling of an area, level or gameplay experience with the music. The music will not be 'synchronized' with the events on the screen. Much of the emotional power of music is lost that way.
In comes adaptive music.
Adaptive music is a unique appearance in video games (and possibly some other interactive media). It suggests that the music responds appropriately to the events taking place in the game. Imagine, for example, walking through an empty building at night. The music is very calm and has some suspense. While you are walking, you unknowingly move closer to a certain room in the building, and the music gets more eerie and dark. You finally find a door that you have to pass through to advance to the rest of the level, but the music is now so spooky you know something is waiting for you on the other side. Then, as you move towards the door to open it, two monsters jump at you from the shadows on your sides. Now the music becomes upbeat and dramatic, as you defend yourself as best as you can against these attackers. After dispatching them, the music becomes calm and soothing while you have time to take a breather..
As you can see in the above example, instead of just using one suspenseful track for the whole level, using adaptive music enhances the impact of the events in the game just as a movie soundtrack does for a movie. From a game designer's perspective, adaptive music can be a tool with which to communicate to the player of a game, just like the graphics. The player may learn, for example, that when a certain type of music starts playing it means there are enemies nearby. Even if the graphics are available and being used to communicate a situation, adaptive audio can be a means to enhance that communication with an audible dimension, and steer the players' emotions in the direction you want. The experience of walking through a dark forest at night will be completely different if there is scary music playing then if there were soothing music playing, for example.
Composer Guy Whitmore uses the following analogy to describe adaptive music:
"In a sense, linear music is to pre-rendered animation as adaptive music is to real-time 3D graphics." 
Instead of creating a 3-dimensional movie and playing it back for someone, a 3d game creates the 3-dimensional world onscreen in 'real-time' while the player is walking, racing, etc. around in it. Adaptive music does this with the game's music. Instead of creating a linear score and playing it back to the player, the music is created or (put together) while the player is playing the game.
Of course, having a game play random pieces of music on and off, alone or together, loosely based on changes in the game state can not be called adaptive music (instead, I would call that interactive music). The music has to fit the narrative of what is happening in the game and add to and expand the visual representations of those events.
There are several ways to create adaptive music, but choosing an adaptive soundtrack for a game always means the music will have to be created differently from linear soundtracks. Instead of writing a regular song, short pieces and/or layers of music (percussion loops, different melodies and instruments) must be created as separate audio files, while fitting together perfectly so they can be played at the same time or seamlessly (without a pause) one after the other, depending on what is going on in the game. These pieces can vary in length from a single note to several minutes, depending on how much adaptability the soundtrack for a specific game needs. Guy Whitmore calls this the spectrum of adaptability:
"On one end of the spectrum is linear pre-rendered music, and on the other is music that is completely game-rendered." 1
The definition that follows out of the previous text is this one: Adaptive music is music that responds appropriately (or adapts) to the events in a game.
 Guy Whitmore , Design With Music In Mind: A Guide to Adaptive Audio for Game Designers (Gamasutra.com, 2003)
What about sound effects?
We should make a clear distinction between sound effects (gunshots, screams, etc.) and music: Sound effects are adaptive almost by nature, as they are only triggered when the game code (and thus the game designer) indicates it is the right moment to do so.
If a player moves towards a monster in a game world and the growling of the monster becomes louder and more intense, this is not adaptive music. The growling simply becomes louder because the (volume of the) sound is based on the 3D-location of the monster in the game world, meaning the closer the player gets to the source of the sound effect, the louder it is played.
The growling gets more intense because the monster senses the player is getting closer through its programmed AI (artificial intelligence).
Sound effects (especially 3 dimensional ones) are always adaptive, as they respond appropriately to the actions of the player and the events and situations in the game world.
Adaptive music back in the day?
Now that we've defined what adaptive music exactly is, let's take a quick look at its use in the past.
Adaptive music is really almost as old as video gaming itself. Many old games already had some degree of adaptability in their soundtrack. One famous example that comes to mind is the change in music in Super Mario Brothers (1985) for the Nintendo entertainment system (and subsequent Super Mario games) whenever Mario or one of the other playable characters picks up a star: The star gives the player invulnerability and the power to kill enemies by touching them, and a special, more intense song plays for the duration of its effect.
Another example from back in the day is Mortal Kombat (1993): At the end of the final round the winner is given the option to finish off his opponent with a deadly fatality, which has to be performed in a few seconds. An extra dramatic loop, which raises players' and spectators' expectations, is played during these seconds.
In these examples the music simply changes from one tune to another. Though the effect can not be denied, this can hardly be called adaptive music.
Over the years, more audio designers started to experiment with audio that responded to events in the game (calling it interactive audio). The 1998 game Gex: Enter the Gecko changed the music depending on the number of enemies on the screen. In one level the music stops for a moment when the player kills all the enemies on the screen. In another level (with a horror theme) the harmonics of the music (which is eerie, horror-type chamber music) are pitched upwards depending on the number of enemies on the screen, making the music more eerie as more enemies appear on the screen. Gex: Enter the Gecko had a lot of these types of adaptations to the state of the game in the music.
Enter the Matrix (2003) used orchestrated music cut into short segments (most of them a couple of seconds long). The game would seamlessly switch between these segments depending on what was happening in the game. Apart from being a little repetitive (if the situation in the game didn't change, neither did the music), this gave the soundtrack somewhat of a movie soundtrack feel.
These are all relatively simple example of adaptive music. It can get rather more difficult depending on how much adaptability the game soundtrack should have (or where on the 'spectrum of adaptability' the soundtrack should be).
A modern adaptive soundtrack can be made up of hundreds of short musical parts that can be played together and/or one after the other depending on a wide range of possible game-states (the state of the game, e.g. what is happening at a certain moment). Composing music in this way requires a composer to look at the music in a different way than he or she may be used to, and that may be one of the reasons why adaptive music is not very common yet: Composers may find it hard to get into. The idea of regular music that has a flow of emotions must be let go of, and the idea of music adapting to the events in the game must be embraced. A thorough understanding of how the music will be handled by the game engine (the code that creates the game as it is played) is needed, as it will be the game engine that puts the different parts of the adaptive soundtrack together depending on game-states.
So why do some people call it interactive music and some adaptive? What's the difference between the two terms (if any)?
"By "interactive music", I don't mean simply music being used in an interactive application like a game. I mean music that responds to the state of affairs the user is experiencing." 
Though I mostly agree with this definition, I think the words interactive music should be switched for adaptive music.
Let's look up the word interactive:
From the Cambridge University online dictionary:
1 : describes a system or computer program which is designed to involve the user in the exchange of information:
an interactive game/video
This is an interactive museum where children can actively manipulate the exhibits.
2 : involving communication between people:
interactive teaching methods
From the Merriam-Webster online dictionary:
1 : mutually or reciprocally active
2 : of, relating to, or being a two-way electronic communication system (as a telephone, cable television, or a computer) that involves a user's orders (as for information or merchandise) or responses (as to a poll)
So the adjective interactive merely implies that there is a two-way communication between two people or a system and a user. Any communication will do.
This means even the old Tetris game for the Nintendo Game Boy had interactive music: there was a menu where you could change the song that was played during the game, and depending on what choice you made, a different song was played!
Interactive music can appear in all interactive media that have music: All it does is change the music in response to actions of the user.
Now let's look at the word adaptive:
From the Cambridge University online dictionary:
1 : possessing an ability to change to suit different conditions
From the Merriam -Webster online dictionary:
1 : showing or having a capacity for or tendency toward
This means adaptive is an adjective that indicates the subject has a tendency or capacity to adapt:
To make fit (as for a specific or new use or situation) often by modification
So music can be called adaptive if it adjusts to environmental conditions. In video games this means the music adapts to the conditions of the game (the game state). The subtle but important distinction with interactive music is that the word interaction suggests that the music changes in response to the actions of the user (by giving him a menu where the music can be changed, for example), but that this music does not necessarily have to be suitable for the game state. Only if the changes in the music fit the events in the game can the music be called adaptive.
Another distinction is that while the word interactive implies two-way communication, adaptive music is really one-way only communication: From the game (designer) to the player. The music reacts directly to the 'environmental' conditions, in this case the conditions of the game itself, in a way that has been designed by the game designer. The player does not choose to change the music, and does not press certain buttons in order to change the music. The player only plays the game. It's the game designer that controls how the music works, in order to influence the experience the player has while he plays the game.
Adaptive music is always interactive, as the music directly or indirectly responds to the input of the user (there can not be any adaptive music if no one is playing the game). Interactive music is not always adaptive, however, as music should only be called adaptive if it responds to and anticipates gameplay, and not if it just responds to user input.
Think of a player walking through a scary forest at night (in a game, obviously). The music starts to get spookier as the player walks deeper into the woods, because there is a big monster at a clearing ahead. The player does not know there is a monster waiting for him, but the game (designer) does! The music is interactive in this example because it changes as the player moves around in the game world. This is the direct response to the user input. The music in this example is also adaptive music because it gets spookier as the player gets closer to where the monster is, heightening the player's anticipation and drawing him deeper into the gameplay moment. This is an indirect response to the actions of the user, and in fact even a way to communicate to the player something scary is up ahead (even though it may be a subtle, subconscious message).
Pretty much every game has interactive music, as the music usually changes when you reach the next level or fight a boss, etc. Adaptive music is only the music that changes without the player needing to know why (or even noticing it consciously), its sole intention is to make the music fit the events on the screen.
Interactive music may be a good way to describe the workings of the music in the game code, but adaptive music says more about how the music sounds when you are playing the game, and about how the composer will have to try and make the music work.
 Kurt Harland, Composing for Interactive Music (Gamasutra.com, 2000)
Why should we use adaptive music in a game if writing and programming an adaptive soundtrack is more complicated than creating a linear soundtrack? Many composers may not even have written adaptive music before and will need to adapt, as it were, to the specific techniques needed to create a successful adaptive soundtrack. Many programmers will also have no experience in implementing adaptive music and will therefore need extra time to create and implement it, making it more expensive.
However, the pros of using an adaptive soundtrack far outweigh the cons (if it is done right).
A good adaptive soundtrack can make the experience of playing a game much more enjoyable and memorable because of the effect music has on the emotions of people. How is it that adaptive music can draw players into a game so much better than a regular soundtrack?
First of all the attentive player will notice that the music fits the events in the game perfectly and will respect and enjoy the game the more for it.
Studies have shown that during emotional moments the brain takes in ones environment very precisely, including what (if any) music is being played . So if you finally manage to beat a huge and powerful monster, or clear a very difficult puzzle, you will notice very strongly the music and sounds that accompany this event. If this music does not fit the mood of the event, some of the emotional impact of the game on the player will be lost, while the right music will strongly enhance the emotional experience and make sure that you will remember it.
Then there is something known as suspension of disbelief. Suspension of disbelief is a term used to describe how people let go of their normal ideas about whether things are realistic and logical in order to enjoy a work of fiction, such as a novel, a movie or a book. The television show Star Trek, for example, requires the viewer to 'suspend their disbelief' about whether it is possible to travel through space at light speed or to instantly teleport objects and creatures over long distances. Once the viewer accepts these facts as realistic within the story of Star Trek, he can start to enjoy the show.
That same suspension of disbelief is needed in most video games, unless they depict abstract events (or are somehow ultra-realistic).
So how do we make players forget a game is unrealistic and make them believe they are driving a super fast sports car through the center of Los Angeles at 200 kilometers per hour? Or that they are a sword-wielding, magic casting hero in an ancient kingdom? By being as consistent as possible within the fantastic world of the game.
Let's compare with graphics again. Take a racing game, for example; Having the cars in the game actually sustain visible damage when they hit each other or crash into a wall will make the experience a little more believable, while crashing a car into a wall at high speed without the car so much as getting a scratch on the hood will make the player laugh, thinking to himself: "That's crazy, I drove my car into a wall and it isn't even damaged".
In a sword fighting game, if the player has bloody wounds in the places where he's been stabbed, it will look a lot more realistic then if being stabbed had no effect at all. Having the graphics respond appropriately to what is going on in the game will make it easier for players to maintain their suspension of disbelief, because they are not constantly reminded that it's "just a game" they're playing.
So if the graphics should respond to what is happening in the game, why let the music fall behind? If the player gets stabbed with a sword repeatedly and becomes heavily wounded, isn't it logical to make the music sound more tense and perhaps more dramatic? This seemingly obvious detail of audio design can "add emotional depth and soul to scenarios and help maintain the suspension of disbelief that is so crucial for players."
Whether the player consciously notices it or not, adaptive music will draw him deeper into the game and elicit more emotional response. A regular, linear score, on the other hand, can actually deduct from the gameplay experience. Any piece of music that is not extremely simple or ambient will have calmer and more active parts, emotional ups and downs, etc. If a piece of music is just played in a regular, linear, fashion, chances are the calmer and more active parts of the song are not played at the appropriate moment (namely, when the gameplay has a calm or more active moment respectively).
Music that is not appropriate for the gameplay and the events in the game can distract the player and destroy the suspension of disbelief. On top of that, hearing the same track over and over again in a certain area or level can easily get on peoples nerves, while good adaptive music usually will not sound exactly the same each time you play the game.
Some games will benefit more from an adaptive soundtrack than others. In games with a lot of story-telling, such as role-playing games or adventure games, the emotional involvement of the player to the story is very important. Even with good gameplay; if the player does not enjoy the story, he will most likely stop playing the game. And just like in movies, music fitting the events on the screen will make the story have much more impact.
Another example of a genre that really benefits from adaptive music is the (survival-) horror genre. This genre relies on tension and atmosphere to make the game enjoyable for players, and adaptive music can greatly enhance these.
Other games may not have a great need for an adaptive soundtrack. In a racing game, for example, a few good normal upbeat tracks that are nice to race to will do the job.
On the other hand, it is not hard to imagine adaptive music in a racing game. The music could get more exiting as the end of the race draws near, or as two cars are dueling each other for pole position.
In the end, there is always some degree of emotional involvement of the players in any game, and an adaptive soundtrack will enhance that involvement, drawing players into the game easier, enhancing the gameplay and making the experience of playing the game more memorable. This in turn will result in better reviews and better sales for a game, which will make up for the extra investment it takes to create the adaptive music.
 Reinoud de Jongh, Rillingen over je rug: Hoe muziek ons brein bespeeld (Psychologie magazine, January 2006).
 Guy Whitmore , Design With Music In Mind: A Guide to Adaptive Audio for Game Designers (Gamasutra.com, 2003)
So how does one create adaptive music that suits the needs of the game design? There are several ways of creating adaptive music that have already been tried and tested, and there is a lot of room still for new techniques. There is one thing, however, that is always important in the creation of an adaptive soundtrack:
For a regular soundtrack, sometimes the composer only needs to know the general feeling and idea for the different tracks and can then go on to compose the music on his own. With adaptive music, however, the composer must keep in mind the details of the different events and states in the game and what kind of changes in the music they trigger. Depending on the game design and the game's musical needs, a different way of creating adaptive music may be needed (think about the spectrum of adaptability mentioned in chapter 1). A close collaboration between the game designer and the composer is therefore absolutely vital for the creation of a good adaptive soundtrack.
The game designer often has general ideas about what kind of music should be used for what situations, and the composer can add more details to that vision, adding more specific ideas to the audio design (about what kind of music works well to convey certain moods to the player, for example). Together these ideas result in a detailed audio design, which can also be used to communicate to the programmer(s) what kind of events and states in the game are going to trigger changes in the audio.
Communicating with the programmer(s) (responsible for the audio engine) is obviously very important as well; there are different ways of creating adaptive music in a game and they require different coding.
The programmers will need to know what events and states of thing in the game are important to the music. If the music needs to change when the player's life is lowered, for example, the game code needs to send a signal to the audio engine when this happens. With complicated adaptive music, there can be hundreds of states and events in the game that influence the music, and the programmers need to know exactly what they are.
Ideally, the programmers will create a piece of software (or sometimes an existing program can be used) that allows the composer to easily edit what happens to the music under what circumstances, without having to change anything in the actual game code. This software should give the composer access to all the different states (and state-changes) in the game, and allow him to set for each of those states whether and how they will influence the music.
For example: In the options for the state "Player's life drops below 50%" the composer is able to set that a new piece of music starts playing, and/or that a piece that is already playing should have it's volume raised, and/or that at the end of a current piece there should be a transition to a new piece, etc.
Finally, the composer should be able to continuously test the adaptive music in the game to see if it has the intended effect, changing the music and the states to which it responds where needed, and then immediately testing it in the game again.
Currently, the IASIG (Interactive Audio Special Interest Group) is working on a piece of software that will allow composers to edit their adaptive music in the way just described, called IXMF (Interactive eXtendable Music Format). The interesting thing is that this software will be platform-independent, which means it can be used to work on soundtracks for PC games, Xbox games, Playstation games, etc. (more on this in chapter 5).
The walls between composers, game designers and programmers are slowly disappearing as adaptive music is embraced more and more by game developers. While with a linear soundtrack the composer only needs to know what the general themes for the music are, to create an adaptive soundtrack the composer needs to know how the game is going to be played (what the flow of the gameplay is like). At the same time, he also needs to understand how game engines will handle the different ways of creating adaptive music. That is not to say composers should study game design or that programmers should study music composition, etc. The idea is that everybody involved with the music in the game will have to work together closely in order to make an adaptive score work well.
Digital audio or MIDI?
Normally digital audio is used to create game soundtracks, but MIDI used to be very common as well, and it is very suitable for adaptive music. Both have their pros and cons.
Wave files are full-quality digital audio files, which can be compressed to formats such as MP3 or OGG to save disk space (at the cost of some quality). The good thing about wave files is that they can come from any source, meaning you can use live recordings of an orchestra, home-made electronic music, recorded voice, etc. However, the music in a wave file is fixed, and can not be altered anymore. This means that to get a high level of adaptability with wave files you need to create a lot of separate files for different parts of the music (such as several string parts, different types of percussions, etc.). This means the size of the audio included with the game will increase, and that can be a problem for some games (such as downloadable games).
MIDI-files do not contain any actual audio. They only contain information about when to trigger notes for different instruments, and about changing the pitch, volume, velocity and a lot of other parameters for notes. MIDI files are extremely small (several hundred times smaller than a MP3 file), so handling a MIDI-signal requires hardly any disc-reading or calculations from the computer.
The actual audio comes not from the MIDI-files themselves, but from separate audio files. Devices such as Sony's Playstation or Nintendo's Gamecube have build-in synthesizers that can be triggered by MIDI files, so instead of including a piano song with a game, it is possible to instead include a MIDI-file and use the devices' piano synthesizer to play the song. If the sounds available on the platform are not sufficient for the soundtrack the game needs, digital instruments (a collection of samples that can be played back by a MIDI file) can be included with the game.
MIDI makes it possible to create music that is adaptive on a very detailed level (as the game can use the MIDI signal to trigger single notes and change the pitch of a note, etc.). This makes MIDI especially handy for adaptive musical events that need to respond to gameplay fast. If a dramatic string chord must be heard when the player shoots a monster, for example, the audio must be heard before the visual cue (the dying monster) is gone.
Timing the adaptive musical events and transitions is also a lot easier with MIDI because the number of beats and tempo of the music can be included in the signal.
If there is not much adaptability needed in a game, fading between a few digital audio files may be good enough. And if the build-in synthesizer on the platform has good enough sounds, there is no reason to create your own audio files.
But in all other cases, combining MIDI and audio files will give the best results. One or more audio files can form the basis of the music (for example: a slow ambient track that constantly plays and some percussion that will fade in when enemies appear), and MIDI can be used to add adaptive detail to it (adding for example a piano melody that intensifies with more notes and chords as the player loses more and more life). To save disk-space, the digital instruments available on the platform should be used as much as possible. Custom samples can be included with the game when necessary.
To create an adaptive soundtrack, transitions between different pieces of music are needed. These transitions can be implemented in different ways:
Silence Between Tracks
New jobs in adaptive music
As new production processes appear to create adaptive music for the next generation of video games, new jobs and job descriptions in the game audio production and design field are needed. The following tasks are essential for the creation of adaptive music:
These are the tasks, not necessarily the number of people. In smaller development teams one person can take on several of these tasks (and related tasks such as designing sound effects).
Finally, some important things to consider when creating an adaptive soundtrack (or a regular one, for that matter):
A video game soundtrack should have a common theme or idea, something that ties the whole soundtrack together.
There are a lot of situations in games where it is better to have no music at all (only ambient sounds). This will make the parts that do have music stand out much more and really have impact on the players' emotions (which is what you want to use music for in the first place).
If you spend a good deal of time designing the soundtrack and players turn down the volume it means you did something wrong.
So what does the future have in store for game designers and composers working with adaptive music and for the gamers that will buy their games?
At the moment there are several projects in which composers and game designers are working towards developing new tools for composing adaptive music. There already is a tool by Microsoft called DirectMusic which gives composers the ability to set in detail how a set of sound files should be handled by a game, but it's a very complicated program that composers without any knowledge of coding will find difficult to use.
Very promising is the development of IXMF (Interactive eXtensible Music Format) by the IASIG (Interactive Audio Special Interest Group). This is a format for storing all kinds of media files (wav, mp3, MIDI, etc.) along with information about how and when those files should be played back in a game. IXMF is a cross-platform format, which means it can be used on different platforms, such as the Playstation or the PC.
A tool like this can make creating adaptive scores for games much easier, as the composer can use the programs of his choice to create the music and include information about how and when the files should be played back and mixed together, and the music can then be played correctly by all systems. This will save a lot of time in the production of cross-platform games.
It is always difficult to get competing companies (such as Microsoft and Sony) to accept the same standards for their platforms, but the IASIG is a group of respected game audio veterans, so they may very well be able to make the IXMF-standard a reality.
Game developers and publishers are still hesitant to allow for more budget to create adaptive music, as they are not yet convinced it will help increase the sales, and in their eyes creating a game is ultimately about making money. This is likely to change in the near future, though, as game critics (and consumers) are beginning to recognize the value of adaptive music. The quality of the level of entertainment video games can offer is rising as technological possibilities are expanded, and all available means are used to draw players into a game emotionally: professional storywriters and actors are hired, graphical standards are raised, (online) multiplayer possibilities are expanded, etc. In the same way, better ways of integrating music in games are needed, and adaptive audio is one of the techniques that can do this (and could for many years already, but simply wasn't recognized or appreciated as such).
As for the people that buy and play the games: They can expect to play increasingly more games that offer a much more immersive aural experience, heightening the emotional immersion and making the game more enjoyable altogether.
Bernstein, Daniel, 'Creating an Interactive Audio Environment', Game Developer, 1997
URL (June 2006): http://www.gamasutra.com/features/sound_and_music/111497/audio_tips_05.htm
Bridgett, Rob, 'Interactive Music', Computer Arts Magazine, 2002.
URL (June 2006): http://web.archive.org/web/20021203015700/http:/www.sound-design.org.uk/interactive.htm
Cambridge University online dictionary.
URL (June 2006): http://dictionary.cambridge.org/
Holland, Norman N, 'The Willing Suspension of Disbelief: A Neuro-Psychological View', Psyart, 2002
URL (June 2006): http://www.clas.ufl.edu/ipsa/journal/2003_holland06.shtml
Interview with Guy Whitmore (By Alexander Brandon), IASIG, 2002
URL (June 2006): http://www.iasig.org/pubs/interviews/guy_whitmore.shtml
Jongh, Reinoud de, 'Rillingen over je rug: Hoe muziek ons brein bespeeld', Psychologie magazine, January 2006.
Law, Linda, 'Introducing the Interactive XMF Audio File Format', Gamasutra.com, 2003
URL (June 2006): http://www.gamasutra.com/resource_guide/20030528/law_01.shtml
Merriam-Webster online dictionary.
URL (June 2006): http://www.m-w.com/
Miller, Steven, 'Producing Interactive Audio: Thoughts, Tools and Techniques', Game Developer, 1997.
URL (June 2006): http://www.gamasutra.com/features/sound_and_music/111497/interaudio3.htm
Ross, Rob, 'Interactive Music...er, Audio', Gamasutra.com, 2001
URL (June 2006): http://www.gamasutra.com/resource_guide/20010515/ross_01.htm
Schmidt, Brian, 'Interactive Audio Development: Where the Heck Do We Go From Here?', Project Bar-B-Q speaker, 1999
URL (June 2006): http://www.projectbarbq.com/bbq99/bbq99bs.ppt
Whitmore, Guy, 'Design With Music In Mind: A Guide to Adaptive Audio for Game Designers', Gamasutra.com, 2003
URL (June 2006): http://www.gamasutra.com/resource_guide/20030528/whitmore_01.shtml