If you play two beat patterns versus each other at different, but similar tempos they slide against one another... in effect they go in and out of "phase." I'd never really listened to any example of this at length until I started picking up some Steve Reich tunes on Lala (see for example "Piano Phase".
I never have really tried this myself but for grins I put together a bidule for doing just that. What you'll hear in 122v120-rpeg-rotator-shifty.mp3 are two horn lines. One is running through quarter note triples at 120 beats per minute. The other horn line is running through its triples at 122 bpm. On top of that is an arpeggiated flute line. The arpeggiated line is coupled to the level of correlation between the two other lines. Initially the flute part plays more loudly the less-correlated the two horn lines are. However, that line itself is designed to shift in and out of phase with respect to the correlation metric. It gets complicated fast. I have put three different patterns to use in the arepeggiator itself so you should be able to hear that as well. For grins one of the horn lines (the one which also drives the arpeggiator) is cycling back and forth between an i and iv type chord base. I don't think I've yet listened to the entire thing repeat just yet :)
If you can handle Reich or Glass works of similar technicality you might actually enjoy it. I've started using this as an element of a bigger piece.
For a more pure and easy to digest example... try 121v120-triplets.mp3. That is a two line piano version which goes in and out of phase more slowly so it is easier to discern what's going on. The notes used are C,E,G in each of the piano lines (one an octave up from the other) but because they shift against each other there are arguably 6 different modes in a whole cycle.
Sunday, April 25, 2010
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