Firstly, I would like to say that I am
a big fan of interactive music in games. But I would also like to
point out an important issue that a lot of marketing people, journalists
and even game producers forget: Interactive music in games can never
work exactly like it does in the movies. Why? Well, it's very simple,
and here it is: In the movies, the music suggests what is going
to happen, not what has already happened.
In other words, when the bad-guy appears
around the corner and starts shooting at you, it's really too late
to say anything about it musically. Listen to the music in movies
and tv dramas, and you will notice that the music always tells of
something that might happen soon - not what has just happened.
Still, we have to try. Of course, although
the music may change a bit too late, that is still better than having
it not change at all.
DirectMusic (TM) is a system developed
by MicroSoft, and is probably the most feature rich way of creating
interactive music now. It was made for PC, but being a Microsoft
product, I would be very surprised if the same system didn't also
work on the X-Box. (At the time of writing this, X-Box audio
features aren't clear yet).
DirectMusic can be interactive in many
ways, and the game code can control various aspects of the music.
It can jump to different parts of the song - it can change the tempo,
change the key/chords of the music, and even play little
extra "tunes" (called Motifs) on top of the background
I'm actually working on a project in DirectMusic
right now, and although it's a bit complicated, I'm quite enjoying
it. It's fun, and it's perfect for creating music with that "classic"
The latest version of DirectMusic (for
Direct-X 8) can also do neat things like a low-pass filter
on the instruments (to create those cool analog-sounding
Seeing as how DirectMusic is done with
sequences and samples, it will never sound as "polished"
as a full-on CD recording. You can't have a real guitar solo in
there or anything like that. It's basically "chip sound",
but with samples.
DirectMusic also requires very close connections
between the game code and the musical content, and therefore also
needs very close cooperation between the musician and the audio
programmer. A lot of the changes in the music requires both that
the musician creates the actual content, and then the audio programmer
has to implement it into the game.
Because of the complexity, it probably
also takes a bit longer for the musician to create the music, compared
with straight-forward music.
If you are interested in DirectMusic, please
check out this DirectMusic demonstration
that I have made.
Another way to make "interactive
music" would be to use a so called "tracker" program
(like "FastTracker 2"). "Unreal" is a
good example of a game that used this system (great soundtrack by
Alexander Brandon). The "tracker" is a music composition
tool that lets you store a set of custom samples in memory, and
use a set of sound channels (much like a multitrack tape) to trigger
these samples at various volumes, pitches, and other special effects.
The music can then be built up in blocks of 2 or 4 bars,
and these blocks can be played in a different order, depending on
the game conditions. This obviously will not produce any real different
music every time - afterall, it's going to be the same snippets
of music every time, just played in a different order. But it does
at least give you the option to, for example, let the music take
a more sinister mood when the player starts to move his armed forces
- or whatever.
The downsides to this system are: (1)
although it sounds far better than General MIDI, it still doesn't
sound quite as big and glossy as a CD track or audio streaming .(2)
Writing the music in this format is time consuming; as it
for the most part has to be "programmed" with numbers
and letters, rather than recorded with keyboards and guitars. (3)
It requires a fair amount of programming to implement this system
into the game, especially if you want it "interactive".
I was actually working on a big interactive
soundtrack for a game called "Pig Detective", using
this system. Until, unfortunately, the whole game was cancelled,
and all my work had been in vain (I hate when that happens!!!).
The code for this music system was already up and running on the
PlayStation, but not on the PC yet - and I guess they never got
around to it before the game got cancelled. But if you want to hear
what some of my "Pig Detective " music sounded like, created
with "samples, patterns, numbers and codes", then
go to my credits page on http://www.lynnemusic.com/credits.html
and listen to the mp3 samples from "Pig Detective".
Yet another way to do "interactive"
music is to use audio-streaming of multiple streams. The musician
would then compose the music using all his music gear, full studio
setup; he can play guitars, bring in singers, real
violin players and whatever time and budget allows for. This
music is then sampled into long sample-files at, typically, 22khz
16-bit stereo. The sample-files are stored on the CDROM or harddisk,
and played from there to the speakers, via a RAM buffer. When the
game condition changes and different music is needed, a different
sample can start to stream from the CD/harddisk, and be crossfaded
into the old music. (I.e. the "old" music fades out at
the same time as the "new" music fades in, over a second
or so). For the two music pieces not to artistically crash totally
with eachother and produce unbearably disharmonic results, all the
music must of course be written in the same basic key, or, alternatively,
be similarly dissonant. But this doesn't represent any major problem
if the composer knows about it from the start.
The up-side about this is the fact that
it sounds great, and that it doesn't require a whole lot of programming.
The downside is the fact that the audio files take a lot of disk-space,
so you can't have this in downloadable games; you can only use it
if the game comes on a CDROM. For 22khz 16-bit stereo audio streams,
allow approx 5 MB per minute of music. For better sound quality,
go with maybe 26 Khz or even 32 Khz. If you are an "audiophile"
and only the best sound quality is good enough for you, then go
44 Khz - but this will cause a greater strain on your CPU overhead.
Of course, there are still other music
playback systems. General MIDI is one. It's getting a bit old actually,
the only up-side to this system now is the fact that the files are
really small, and I belive playback is already built into Direct-X
(?) although I'm not absolutely sure about this. But it sounds dated
and cheesy. Most people these days would expect General MIDI
music only on low-price budget game releases and perhaps kids' games.
Redbook audio / CD audio
Finally, there is redbook audio (which
is just a fancy word for "normal CD audio") and
this is probably the most common format these days. Up-side: It
sounds great, the only limitation is the quality of the producer
and his budget / quality of studio equipment. Down-side: It is totally
linear - with no room for "interactivity" - and it takes
a lot of disk-space (Allow approx. 10 MB per minute of music).
One other "gotcha" about playing normal CD audio tracks
is the fact that the entire PC "halts" for a moment or
two when the CD drive seeks to a new track on the CD!
So what's best for us and our game?
Here's an important point... before
a composer is hired to write music for your game, you need to figure
out the music playback system. If the composer starts writing something
for audio-streaming, it can't be "transformed" to tracker-format
or General MIDI or whatever later on. So if the composer is in the
middle of the project, and the music playback system changes, the
composer is basically back to square one and he'll probably charge
you for his wasted time. Or at least, he should.
So it's a good idea to figure out the
music playback system first. Ask yourself these questions:
game going to be on CD, or is it going to be a "downloadable"
game? If it's going to be downloadable, forget streaming and CD
audio - go for DirectMusic, General MIDI or tracker music.
more important: How interactive the music is, or how cool/professional/glossy
the music sounds? If the professional/glossy sound is most important,
forget DirectMusic and General MIDI - go for audio streaming or
a lot of music have to be written over a short time? Will the composer
be in a hurry? Then do him a favour and rule out "tracker"
format. It takes a lot of time to write music using numbers and
want to pull out all the stops and get yourself a soundtrack that
sound just as good as the TV series Babylon 5, or The
X-Files? Then go for redbook CD audio, or at least audio-streaming
with a high sample rate (say, 32 Khz, 16-bit, stereo). Forget all
other formats. And make sure you get a great composer :-) - not
to mention a budget that can pay his asking price.