The Partridge Family was inspired by the real-life Cowsills, who had a few hits in the 60's, but had all but faded from the scene by the time this series launched in 1970. ABC smartly packaged it as part of a sitcom block that included The Brady Bunch, which was entering its 2nd season, on Fridays.
The mother-son combination of Shirley Jones & David Cassidy headlined, but only Cassidy did his own singing, despite Shirley having some experience in musicals. Studio musicians were used for the rest of the family band. Dave Madden (ex-Camp Runamuck) was cast as the band's manager, Reuben Kincaid, referenced in the show's original theme song, "When We're Singing", which was replaced by "Come On, Get Happy" after the first season.
Also after the first year, there was one minor cast change. Jeremy Gelbwaks was let go, and Brian Forster cast as Chris Partridge. Viewers didn't seem to notice much difference, and Forster reaped the benefits, including landing a side gig, along with TV sibs Danny Bonaduce, Susan Dey, & Suzanne Crough, on Goober & the Ghost Chasers, which also aired on ABC during the Partridges' final season (1973-4). Of course, there's also that misguided offshoot that sent the family into the future, which CBS picked up in 1974, but the less said about that, the better.
Shirley Jones narrated some of the early episodes, like this one:
Too bad the Cowsills and the Partridges never got together. It would've been something to see, even on, ah, Family Feud.