Ray Collins, a singer whose dispute with one guitarist led him to hire another, Frank Zappa, with whom he would go on to form the avant-garde rock group the Mothers of Invention, died Monday in Pomona, Calif.

The death of Mr. Collins, who was in his mid-70s, followed his admission to Pomona Valley Hospital Medical Center a week earlier for cardiac arrest, according to local news accounts.

Mr. Collins entered the national spotlight with the Mothers of Invention, an outlet for Zappa's unique sense of humor and challenging, unorthodox compositions. But his musical beginnings were more mainstream. In the mid-1960s he was singing falsetto in a rhythm-and-blues cover band called the Soul Giants when things soured between him and the band's guitarist, Ray Hunt. He fired Hunt and replaced him with Zappa.

Mr. Collins, who shared a love for doo-wop with Zappa, was the lead singer for the band's debut album, Freak Out! (1966), which mixed satirical lyrics with music that ranged from straightforward rock to atonal experimentation, and its follow-up, Absolutely Free (1967). He quit the band after that recording, though he returned for Cruising With Ruben & the Jets, a doo-wop concept album, and sang on some of Zappa's later recordings. - N.Y. Times News Service