It’s Gonna Rain… is a very heavy piece written in the shadow of the Cuban Missile Crisis, and the voice is a spectacularly moving, intense voice about the end of the world.Around 1964, influenced by his work with Terry Riley on In C and the latter's use of tape looping and delay systems, Reich started experimenting with these techniques as well.
The source material of It's Gonna Rain consists entirely of a tape recording made in 1964 at San Francisco's Union Square.
[2] In the recording, a Pentecostal preacher, Brother Walter, rails about the end of the world,[3] while accompanying background noises, including the sound of a pigeon taking flight, are heard.
Reich decided to exploit what is known as phase shifting, where all possible repeated harmonies are explored before the two loops eventually get back in sync.
During a lecture at the Long Now Foundation, electronic musician Brian Eno cited It's Gonna Rain as his first experience with minimalism and the genre that would come to be known as ambient music.