While working on Six Pianos I also began work on another piece that seemed to grow very spontaneously from one simple marimba pattern to many patterns played by different instruments. Music for Mallet Instruments, Voices and Organ was completed in May 1973, and deals with two simultaneous interrelated rhythmic processes.
The first is that of constructing, beat by beat, a duplicate of a pre-existing repeating musical pattern with the second being one or more beats out of phase with the first, exactly as in Six Pianos. This then triggers the second process of augmentation of another simultaneous but different repeating musical pattern. The first process of rhythmic construction is performed by marimbas against marimbas and glockenspiel against glockenspiel. These rhythmic constructions, which have the effect of creating more fast moving activities in the mallet instruments, then trigger the two women’s voices and organ into doubling, quadrupling, and further elongation the duration of the motes they sing and play. When the marimbas and glockenspiels have built up to maximum activity, causing the voices and organ to elongate to maximum length and slowness, then a third woman’s voice doubles some of the short melodic patterns resulting from the combination of the four marimba players, using her voice to precisely imitate the sound of these instruments (exactly as in part two of Drumming). During the rhythmic constructions in the marimbas and glockenspiels, the metallophone plays long ringing tones for the same duration as the voices and organ. When the voices and organ get longer, so do the tones of the metallophone. However, a bar of steel over an aluminium resonator tube rings for just so long and then decays into inaudibility so that when the voices and organ have reached their maximum length the metallophone then begins playing rippling sixteenth notes, moving as fast or faster than all the other mallet instruments in combination. After these sections where the voices and organ have reached their maximum length (based on the length of continuous tone a single breath can sustain), the marimbas and glockenspiels begin, one at a time, to abruptly move into unison with each other, thus allowing the voices, organ, and metallophone to begin reducing the length of their sustained tones. This paired process of rhythmic construction-augmentation followed by rhythmic unison-diminution occurs four times in sections marked off by changes in key and meter. The first section is in F dorian 3/4, the second in A-flat dorian 2/4, the third in B-flat natural minor 3/4, and the fourth is an A-flat dominant 11th chord 3/4. -Steve Reich