While Detroit and Memphis, by way of Motown and Stax, dominated the sound of soul music in the '60s, the sound of the pre-disco '70s came from Philadelphia. Most of the artists responsible for the smooth, complex, string-dominated sound worked under the guidance of producers Kenny Gamble and Leon Huff, who combined the hit-factory sensibility of their predecessors with the emerging self-conscious R&B artistry found in the early-'70s work of Stevie Wonder and Marvin Gaye. Through this combination, they churned out hit after socially aware hit in the early to mid-'70s, helping to bring a political consciousness—this is probably the only box set in which full-page photos of Malcolm X and Martin Luther King don't seem horribly inappropriate—to some of the catchiest songs around. As this collection's title indicates, the team got its start in the '60s, working on classic tracks by The Intruders and Archie Bell & The Drells. But it was the next decade, and Gamble & Huff's collaborations with The O'Jays and Harold Melvin & The Blue Notes (among many others), that made the duo's fortune, and this three-disc set captures the era nicely. In fact, it captures it to its bitter end: The final disc is an exercise in how far good R&B can be pushed before it becomes disco. Even if, strictly speaking, this doesn't represent the whole story of "The Philly Sound"—Gamble and Huff were the prime movers of that scene, but other Philadelphia music, including G&H collaborator Thom Bell's important work with Spinners, is not included here—this is a remarkable collection.