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  • Student Thesis: Adaptive Music for Video Games

    [07.28.09]
    - David Vink

  • 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.

    Interactive or adaptive?

    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." [2]

    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:

    interactive
    adjective
    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:

    interactive
    adjective
    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:

    adaptive
    adjective
    1 : possessing an ability to change to suit different conditions

    From the Merriam -Webster online dictionary:

    adaptive
    adjective
    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:

    adapt
    verb
    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.


    [2] Kurt Harland, Composing for Interactive Music (Gamasutra.com, 2000)

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