The musicians behind the Partridge Family were top notch, with members from the Wrecking Crew. I believe only Shirley Jones and David Cassidy actually appeared on the recordings.
The music created for the Partridge Family was inspired by the "Sunshine Pop" sub genre which was popular during roughly the 1966-1972 period, epitomized by artists like Mamas & Papas, The Turtles, Young Rascals and the Poppy Family (Terry and Susan Jacks).
I've been on a big "Sunshine Pop" kick lately listening to the KHJ "Boss Radio" archives. What a great time for music it was.