MFSB, officially standing for "Mother Father Sister Brother", was a pool of more than 30 studio musicians based at Philadelphia's Sigma Sound Studios. They worked closely with the production team of Gamble and Huff and producer/arranger Thom Bell, and backed up Harold Melvin & the Blue Notes, the O'Jays, the Stylistics, the Spinners, Wilson Pickett, and Billy Paul. In 1972, MFSB began recording as a named act for the Philadelphia International label. "TSOP (The Sound of Philadelphia)", also known as... [more on Wikipedia]