The Black Eyed Peas’ 1998 debut doubles as a precursor to their world-conquering 21st-century run and a snapshot of the jazz-influenced styles that dominated “backpack” rap in the late ’90s. Over instrumentals and samples woven together into fluid, loose beats, will.i.am, apl.de.ap, and Taboo espouse messages of unity (on the jittery “Joints & Jam”) and positivity (on the simmering “Communication”) while hinting at the globally minded ideas that would fuel their later pop success on cuts like the swaggering “Movement.”