Most of the music released by the label was recorded and produced at Sigma Sound Studios in Philadelphia, with chief engineer and later studio owner Joe Tarsia recording many of the sessions. More than 30 resident studio musicians, known collectively as MFSB "Mother Father Sister Brother", were based at this studio and backed up most of these recordings. Some of these musicians also acted as arrangers, writers or producers for Philadelphia International as well as for other labels recording in the city. They included Bobby Martin, Norman Harris, Thom Bell, Ronnie Baker, Vince Montana and later, Jack Faith and John Usry.