someone asked me recently how I work with
the same for the sound. the simplest is on/off (or off/on, which can be different). but it might also be a sound element with modi -- like an "up" and a "down", and "in" and an "out", a "coming" and "going", etc. i.e. any sound with distinct modes or ways of sounding.
not every composer wants to give up that much control, especially to a choreographer, or to a bunch of dancers -- few of whom are musicians! dancers like to call one another musical, but their skill with sensing sound is rarely on the level of a musician.
i used to think rhythm was the enemy of dance. where ever there is rhythm, there can be no live control, no room for spontaneous changes in the sound environment coming out of the body of the performer. as soon as you have a beat, then you have the expectation that the performers are counting it out -- i.e the usual thing.
but actually, it is not quite that simple. i can think of at least 3 ways that rhythmical music might still be dancer-influenced (or, more to the point, be made to seem dancer-influenced). 1) rhythmical elements can be _initiated_ by movement, i.e. rhythmical elements might be intermittant, and unpredictable. 2) as long as the timing is complex enough, i.e. unpredictable, then non-rhythmic elements can easily slice through a rhythmic field. 3) the source of the rhythm is motion controlled even while the underlying rhythm is not.
but interactivity works in a funny way. you don't actually need a lot
of it for the audience to think (and, more importantly, _feel_) that the
entire mis en scène is sensitized. a few strong interactive
elements at the right moments, and the audience will "perceive"
much more. In the end, many or most of the musical and lighting
elements coming "out of the movement", are actually just good
timing. But the point is -- this feeling of connectedness, or even
synesthesia, is not possible without the motion tracking.
so i typically start by looking for elements that seem to want to be movement-controlled. this can mean starting with a "finished" composition and taking it back apart (reverse engineering it) so that it can be then reassembled live, as it were. or we have also made pieces from the ground up. starting with a single sound and gesture and going from there.
But the point I really want to make here is about why it is interesting.