It was a tape of an instrumental track that only cost $15 and took 45 minutes to complete.

Harry Wayne Casey and Rick Finch had been doing such demo tapes for acts like Jimmy Bo Horne and Betty Wright for TK Records in Hialiah, Florida in 1974. Casey felt he couldn't sing the vocals because it would take someone with a higher pitched voice. 

Before scrapping the tape, they took it to TK Records owner Henry Stone and Steve Alaimo, the label's A&R (Artists and Repertoire) man.  "Steve flipped over it," Casey told Superseventies.com, "and said not to change a thing.”

Casey and Finch figured Horne or another aspiring singer could do the vocal. When the latter--George McCrae--walked into the studio the next day, the decision was easy. It took only two takes for George to complete the vocals. "Rock Your Baby" would become a #1 hit and the forerunner of disco music…