[4] Heartsman was born Johnnie Eastman Jr. in Houston, Texas, and moved at an early age to San Fernando, California.

[4] In his teenage years, Heartsman started working as a session musician, in the studio with a local record producer, Bob Geddins.

[1] His own efforts yielded the instrumental track "Johnny's House Party (Parts 1 & 2)", released by the Music City label, which reached number 13 on the U.S.

He played on Tiny Powell's "My Time After Awhile" and Al King's cover version of "Reconsider Baby".

[1] Over the years, Heartsman wrote songs for Jesse James ("Are You Gonna Leave Me"), Roy Buchanan ("Goose Grease"), John Hammond, Jr. (Got to Find My Baby"), Amos Garrett ("Move On Down the Line"), and several more for Joe Simon.