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The theory behind Steve Reich’s phase music
Steve Reich was experimenting with reel to reel decks when he discovered
their inherent difference in playback speed. His experiments put identical
tape loops in multiple decks and discovered what he later called "phasing."
It appears that the two sounds happen simultaneously, then they appear
to have a slight delay. This delay grows larger until a maximum when the
delay becomes smaller and eventually happen simultaneously again. The entire
process repeats indefinitely.
The process
In this Applet, the "phase" part consists of N measures, and the "reference
part consists of N+1 measures. The two parts will play together and take
the same length of time. Thus the "phase" part must play slightly slower
so that it ends at the same time. Additional beats can be added to the
"phase" part so that it changes its phase relative to the "reference" part.
Instructions:
Select one of the measures in the choice box on the left
(the "reference" measure).
Select one of the measures in the choice box on the right
(the "phase" measure).
Select the number of measures in the phase part.
Use "Beat Number to Land on" to add additional beats to the
phase part.
Or, disregard instructions 1 - 4 and press the random set
button.