Boom bap is an onomatopoeic name: boom is the kick drum, bap the snare that cracks on the second and fourth beats. It describes a style of hip hop production built on punchy, often slightly distorted sampled drums and short loops taken from old records, with little else in the arrangement. The phrase is usually traced to T La Rock’s 1984 track It’s Yours, and KRS-One fixed it in the vocabulary with his 1993 album Return of the Boom Bap, for which he insisted on working with DJ Premier.
The sound is linked above all to New York in the late 1980s and early 1990s, to producers such as DJ Premier, Pete Rock and Diamond D, and to samplers such as the E-mu SP-1200 and the Akai MPC60, whose gritty character shaped its texture. Most lo-fi hip hop and chillhop still rests on a boom-bap pattern, slower and gentler but recognisably the same skeleton.