Kin Vassy recorded ("Yippy-Ty-O-Ty-Aye" on Montana, "That's right folks, don't touch that dial" on I'm The Slime, and also sang on Dinah Moe Humm.) and toured (a grand total of 5 days?) with Frank Zappa (the only known case of someone other than Frank singing the "Yellow Snow" Suite. Kin provided vocal for Over-Nite Sensation.
After leaving Zappa, Vassy was in-demand as a session player, and producer in Nashville, TN. He helped many people with their careers, like Faith Hill, who was his receptionist in Nashville. Vassy died in 1994, of cancer - a great loss to the music world.