Wrecking Crew Universe
While I was recording music for television and radio ads I had to be a member of the AFoM (American Federation of Musicians) to be paid. Every couple of months I would go to the recording department window at Local 802 in New York and pick up a small packet of checks. The amount sometimes was as little as $4, and there could be as many as seventy checks at a time. This process was how you got paid for recordings. Every session was a standard contract. What musician played what instrument on which song. Did they play a second instrument or "double" on the date? The terminology in a session was to "get a line" on the job. As in "he played the maracas, put him down for a line." The copyist and band leader would get additional lines.
A few years ago I came across the AFoM contracts for a talented group of California session musicians known as The Wrecking Crew. The songs recorded are widely considered some of the most well-known songs in popular music. In these contracts were interesting details about many Top 40 hits from the 1960's and 1970's. Often by the same drummer, bass player and guitar player.