We've now covered several ways to create nonrepetitive content. There are numerous other ways to add variability to audio content, including (but not limited to):
ChordMaps (see Chapter 6)
Scripting (see Chapter 7)
Style-based playback (see Chapter 4)
But the most common and powerful way to create nonrepetitive content is in the areas that we've already discussed — particularly using pitch, volume, and duration variability, along with the 32 variation buttons available per Wave Track and Pattern Track part.
Avoiding repetition for sound effects and ambience can be accomplished by using pitch and attenuation randomization in combination with the use of multiple variations (typically each using a unique authored version of a sound's wave or waves — one for each variation). If a sound effect is composed of several different aspects, try varying the timing between them somewhat as well for even more alternatives.
Let's take the classic example of a footstep in a game. Traditionally, you might record five or six footsteps and randomly choose between them every time your character moves forward on the screen. But using DirectMusic, you could break the footstep into its component elements — the sound of a heel, the sound of a toe, and perhaps a separate scuff for the sole of the foot/shoe/whatever. Even if you only record three variations of each, by placing each in a separate Wave Track part, you now have at least 3 x 3 x 3 = 27 unique footsteps. If you add appropriate random pitch range to each element, you have even more footsteps. Now if you create added variations where the actual start time of the various elements is adjusted slightly (the scuff sound comes slightly earlier or later), you've got even more potential "performances" of this footstep, with no programmer assistance required.
For musical variability, consider occasionally adding or removing single instrument lines via silent variations. Changes in orchestration from variation to variation are also a quick way to keep music changing with each performance. Melodic lines, particularly those that are closely associated with a chord progression, can be more difficult to structure convincingly in multiple variations — especially when you stop to consider that every possible variation of a part will have to play properly against every possible variation of every other part. As nonmelodic instruments, drum parts tend to be more straightforward for adding variations to quickly.