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Defining Adaptive Music

April 17, 2007 Article Start Page 1 of 4 Next

What is Adaptive Music?

This section didn’t previously exist. When I originally wrote this piece, I assumed that readers would already know what adaptive music was. I also assumed that they would have some familiarity with the kinds of game implementations that are out there. So, in the introduction, I jumped right into exploring the value of a formal definition, without first introducing the basic idea of adaptive music itself. And, in the body of the article, I focused exclusively on non-gaming examples – figuring the reader would be less familiar with (and therefore much more interested in) these.

As it turned out, the original approach didn’t work at all for non-expert readers. I got some preliminary feedback like: “Wow, interesting piece. But are there any, you know, video game examples of adaptive music?”

So! If you don’t already know what adaptive music is, or how it’s used in games, this brand-spanking-new section is for you. On the other hand, if you are an expert reader, you may want to skip ahead.

“Adaptive music” is a game industry term that seems to have entered general usage in the last ten years or so. (I don’t know who first coined the term.) It replaces the term “interactive music”, which was more immediately obvious, but had some accuracy issues.

If I started talking about “interactive music”, you’d probably immediately know what I was talking about… so actually, let’s start there. (In a minute, I’ll explain why we don’t call it that any more. For now, I’ll use “interactive”, since it’s a bit more user-friendly.)

Making Multimedia Music Meaningful

Interactive music is the game industry’s answer to the Hollywood film score.

At the movies, music has become a powerful tool for clarifying and emphasizing emotional contexts. It complements and reinforces onscreen action and beats. It can add or resolve tension, or create anticipation. It can subtly (or not so subtly) associate intangible aural qualities with different characters, while evoking the spirit of times long past and places long vanished (or yet to come… or never to be).

It would be really cool if game music could complement onscreen action with the same kind of subtlety, depth, and expression. The complication is that, in games, the timing, pacing, contexts, and outcomes of the onscreen action are constantly in flux, depending on the actions of the player.

Is the player winning? How many orcs are left? Is it important that the player just ran out of painkillers? Did the player find the AK47 yet, or are the dragons going to eat the bowling ball before her plate-mail is repaired? How long is this battle going to last? Are the tides turning? Was that hit significant? Or… did the battle start at all, or did the player sneak past with the Cloaking Cloak of Cloaking +2?

Most importantly: how can a game composer score a scene intelligently and compellingly, when she doesn’t know what is going to happen, when?

Film Scores Versus Game Scores

When a film composer starts working, she sits down with a finished, fixed-length, edited scene. She can custom tailor a musical accompaniment to fit the film perfectly, with subtlety, elegance, and grace. (One hopes.) Linear music is composed to match the linear scene exactly.

Interactive music in games attempts to score non-linear, indeterminate scenes with non-linear music. It uses game code and data to track changing game contexts on the fly, and to cue appropriate score responses. It also has to track the current music context, in order to avoid ugly or musically inappropriate transitions or pacing. It’s an interdisciplinary challenge, since game logic synchronization is squarely in the programmer’s domain, while music logic is best left to the composers.

Why Don’t We Just Call It “Interactive Music”?

In most cases, “interactive” music falsely implies direct user interaction with the music. (In some games, this is in fact the case – as in the musical game-play of “PaRappa the Rapper” or “Guitar Hero”.) However, in general, the user should really be concerned with interacting with the game. The music system is supporting the dramatic action by adapting intuitively and discretely in order to remain contextually appropriate. Hence “adaptive” music.

Examples of Adaptive Music in Games

The following survey of examples is by no means comprehensive – it barely scratches the surface. Nor should it be considered representative – the selection criteria was rather sketchy. (By and large these are adaptive music systems that have been presented at GDC lectures, with some arbitrary references to titles I happen to own and enjoy.) But some attempt was made to present a broad sample of important trends, technologies, and techniques.

Totally Games / LucasArts’ “X-Wing” series

The “X-Wing” (PC DOS) series, which debuted in 1993, featured MIDI versions of John Williams and John-Williams-esque orchestral music. Lucas Arts’ patented iMUSE music engine handled sophisticated run-time interactions between dramatic onscreen action and a database of music loops, cues, and transitions. (Evolving versions of iMUSE were also used on a number of later Lucas Arts projects.)

Monolith’s “Blood II: The Chosen” and “Shogo: Mobile Armor Division

These Windows titles (released in 1997 and 1998) featured Microsoft Interactive Music Architecture (IMA) technology – a precursor to the (now deprecated) DirectMusic SDK. [3DSoundSurge01]

DirectMusic provided runtime musical alignment tools, and design-time tools for managing (and auditioning) adaptive music building blocks. Advanced functionality included runtime MIDI variation generation based on composer-designed templates (“Styles” and “Chordmaps”), and standardized methods for switching between context-sensitive content versions via “Groove Levels”. DirectMusic was fully supported in DirectX 7 through early versions of DirectX 9.

The Mark of Kri

Sony’s “The Mark of Kri

In a 2003 GDC presentation, Chuck Doud described custom adaptive music technology and techniques that were developed specifically for this PS2 title. Doud stressed that constant, diligent communication and coordination between programmers, designers, and composers were essential for the interdisciplinary project. The team found that an emphasis on percussive elements and irregular meters allowed for some startlingly fast transitions to remain musically consistent and cohesive. [Doud03] The examples he showed demonstrated some incredibly tight synchronization to on-screen state changes.

Stormfront Studios’ “The Lord of the Rings: The Two Towers

This multi-platform 2002 release was able to mine its adaptive building blocks from hours of recorded orchestral cues for the film of the same name. It is a very interesting case, in which big budget music by a big Hollywood composer (Howard Shore) receives a very ambitious interactive video game treatment. [Boyd06]

Ubisoft’s “Rainbow Six 3

This 2003 Xbox title is a good example of a contrasting approach to adaptive game music, which could more properly be described as adaptive music editing than adaptive music composition. In “Rainbow Six 3”, use of in-game music is much more sparing than in the other examples. The title avoids the wall-to-wall approach in-game music, and thereby sidesteps the challenge of changing musical forms on the fly. Cues are reserved for a small number of special dramatic contexts, which are, in general, designed not to overlap. A good percentage of game-play is not scored, focusing instead on immersive sim sound design elements.

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