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Created by TV vet Bernard Slade and producer Bob Claver and Paul Witt (who had helped turn Bobby Sherman into a teen idol on the nonmusical show Here Come the Brides), The Partridge Family was a fictionalized version of the Cowsills story. The Rhode Island-based Cowsills were a typical garage band made up of four brother that became unique when their mother and seven-year-old sister, Susan, joined the act. Recording an armful of LP's between 1965 and 1971, having hit singles (including "The Rain, The Park & Other Things" and a cover of "Hair"), making numerous TV appearances, and running the musical gamiut from light bubblegum to conceptual rock, the family act was one of the more interesting groups of its day. But by the time Slade became interested in exploring the dynamic of a mom in a teen band, the Cowsills were too old (and other than little Susan, not quite cute enough) to star in the show themselves.
Another reason not to hire a real band was to avoid another Monkee mutiny. This show would unambiguously feature actors (not rockers) with the songs created strictly by studio musicians.