These poised soul harmonizers conquered many genres beyond soul without ever losing their immaculate air. Even the rawer vocals on 1974's “Midnight Flower” arrive ensconced in flowing R&B, while 1969's socially conscious anthem “Stop the World” is as bouncy and tight-knit as their career-making Motown singles. And 1975's “We All Gotta Stick Together” delivers a resounding call for unity with a Barry White–esque smoothness.