MFSB, short for Mother Father Sister Brother, was a pool of over thirty studio musicians based at Philadelphia’s Sigma Sound Studios. They are best known for their instrumental track "TSOP (The Sound of Philadelphia)," which became the theme song for the American music television show Soul Train. The Three Degrees, a vocal trio, often collaborated with MFSB and provided the vocals for "TSOP". Their music, a blend of funk, soul, and disco, was instrumental in shaping the Philadelphia soul sound of the 1970s, which had an enormous impact on the landscape of popular music worldwide.