One of his shows was attended by Cass Elliot, who invited Hendricks to join her and Tim Rose in the New York folk group The Big 3.
The group was successful playing The Bitter End, touring with comedian Bill Cosby and appearing on The Tonight Show.
The group lasted for eight months before Yanovsky formed The Lovin' Spoonful and Doherty and Elliot would become one-half of The Mamas & the Papas.
Hendricks moved to Los Angeles and formed The Lamp of Childhood, which released three singles on Dunhill Records in 1966–67 without success.
He improved his songwriting while with the band, and after leaving it wrote "Summer Rain", a hit for Johnny Rivers, and "Long Lonesome Highway", theme song of the television series Then Came Bronson.