Musique Concrete

In the years before sound recording, music was composed for churches, operas, royal courts, concerts, ballets, and taverns, and the music was either written in whatever was the standard notation or tablature or was passes along orally to the musicians who would eventually perform it.
In 1928 Andre Coeuroy, a French music critic, suggested that, "Perhaps the time is not far off when a composer will be able to represent through recording, music specifically composed for the gramophone". 20th century composer Igor Stravinsky also believed that composers would start creating music solely for recorded media.
In the 1940s French composer Pierre Schaeffer thought that rather than simply notating musical ideas on paper and entrusting them to well-known instruments, he would abstract musical value from the real world sounds he collected. He recorded works specifically for the phonograph and coined the term "musique concrete".
Shaeffer and other musique concrete composers used the equipment typically found in the radio stations of that era, including shellac records, turntables, a mixing desk, equalizers, spring or plate reverbs, and microphones for capturing sounds. They would capture and manipulate the sounds by transposing (using different play speeds), looping (using tape devices when they became available), extracting various portions of a sound, and filtering with EQ to drastically modify the sound from it's original form. They developed specific devices to create and modify loops like the "phonogene" and the "morphophone".
While this music was experimental and often too esoteric to be widely appreciated, it laid the groundwork for some of the music recorded today that captures and manipulates samples...music that's composed only to be recorded.