In 1964, a Black Pentecostal preacher named Brother Walter gave a street sermon in San Francisco's Union Square. A young composer named Steve Reich recorded him on a portable tape deck. The recording was a field document, ethnographic material. It was not intended to be music. Then a machine malfunctioned. Then everything changed.
The Loop
Reich spliced a short section of Brother Walter's sermon into a loop: "It's gonna rain, it's gonna rain." He made two identical loops on two Wollensak tape recorders and played them simultaneously. The idea was to explore the resonance of a single phrase repeated, to let the voice become texture. He wasn't expecting anything structurally interesting. He expected two loops in sync.
The Wollensaks did not run at exactly the same speed. One crept ahead of the other by a fraction of a revolution per cycle — too small to notice at first. Then, gradually, the two identical voices separated. The phrase on one machine slipped a sixteenth of a beat ahead. Then an eighth. The two identical voices began to speak against each other, creating rhythmic interference patterns that neither loop produced alone: hocketing, tremolo, echo effects, a stuttering polyphony that sounded like many voices instead of one.
"I was completely absorbed in the sound. I didn't want to fix it. I wanted to find out where it was going."
The Composition
It's Gonna Rain (1965) was the result: an eighteen-minute piece built entirely from two loops of one spoken phrase drifting apart and then — after the piece has passed through every possible phase relationship — coming back into alignment. The structure is the drift itself. There is no melody. There is no harmony in the conventional sense. There is only the gradual movement of two identical things through time at different speeds.
Reich followed it with Come Out (1966), made from a phrase spoken by a young Black man named Daniel Hamm who had been beaten by police during the Harlem riots and needed to reopen his wounds to produce enough blood to convince the police he needed medical attention. The phrase — "I had to, like, open the bruise up and let some of the bruise blood come out to show them" — is looped, phased, and gradually blurred into pure texture, where the words dissolve into rhythm and the rhythm dissolves into drone. The political content does not disappear. It becomes the acoustic material.
The Lineage
Reich's phasing technique established the formal vocabulary that would run through minimalism, ambient music, techno, and contemporary classical composition. The idea that structure can emerge from the mechanical drift between identical elements — rather than from harmonic development or melodic narrative — is the core innovation.
Philip Glass, Brian Eno, Terry Riley, and a generation of producers working in electronic music all absorbed it in different forms. The loop-based structure of electronic dance music — where tension arises not from harmonic change but from the gradual introduction and withdrawal of layers — is Reich's phasing principle scaled up and stripped of academic framing.
The Brother Walter sermon is fourteen seconds long. The section Reich sampled is three seconds of it. From one malfunctioning tape machine and three seconds of field recording, an entire theory of musical structure materialized. The machine broke. The composer listened. The rest is fifty years of music.