EXCLUSIVE
Jamison's booking manager, Sally Irwin, tells TMZ that Jamison died of a heart attack.
Jamison joined Survivor in 1984 (after they found success with "Eye of the Tiger") but was the lead singer on other classic songs like, "The Moment of Truth" (from "The Karate Kid"), "The Search Is Over," "Burning Heart" (from "Rocky IV) and "Is This Love."
Jamison was also the co-writer and vocalist for the song "I'm Always Here" ... the theme song from "Baywatch."
