One of his songs came to the attention of New York music publishing company Shapiro Bernstein, who started to employ him as a staff songwriter.
The duo wrote several Top 10 songs for Frankie Valli and The Four Seasons, including "Working My Way Back to You" (also a hit for The Spinners in 1979, and in Ireland for Boyzone in 1994), "Opus 17 (Don't You Worry 'Bout Me)", and, with Bob Crewe, "Let's Hang On!".
In 1965, Randell and Linzer wrote and produced most of the songs for the R&B girl group, The Toys, including their singles "A Lover's Concerto" (adapted from Minuet in G major, a classical music piece), and "Attack!"
Linzer and Randell wrote two songs recorded by The Monkees, "I'll Be Back Up On My Feet" and "The Day We Fall in Love", and "Penny Arcade" by The Cyrkle.
In the late 1960s and early 1970s, Randell worked in A&R for several companies, including Epic, RCA, and Frank Zappa's DiscReet Records, for whom he produced Tim Buckley's album Sefronia.