Boom-bap is the sound of golden-era hip-hop — A Tribe Called Quest, J Dilla, DJ Premier. Mechanically it's just the basic backbeat with a specific kick pattern (boom · bap · boom-boom · bap = kick 1, snare 2, kick 3 plus &-of-3, snare 4) and a laid-back time-feel: the snare hits arrive a hair late, just behind the click.
The notation below shows the geometry. The feel — the slight drag on the backbeat — is something you have to add yourself. Play these grooves with the metronome, then deliberately push the snare a few milliseconds behind the click. That tension between hi-hat and snare is the whole sound.
Exercises
1 — The Backbeat (Square)
Plain backbeat at hip-hop tempo. Right now everything lands square on the click. Lock to the metronome — once we add the boom-bap kick and the laid-back feel, you need this to be your default.
2 — The Boom-Bap Kick (Add & of 3)
Kick on 1, 3, and & of 3. Boom · bap · boom-boom · bap — say it out loud, that's the rhythm. This is the most transcribed kick pattern in hip-hop.
3 — Add Ghost Notes Between Snares
Soft snare ghost notes scattered between the loud backbeat snares — barely audible, a 4-to-1 volume ratio between the loud snares (on 2, 4) and the ghosts. This is what makes a programmed-feeling boom-bap groove feel alive when played live.
4 — Now Drag the Snare Behind the Click
Same notes as exercise 2, but now play the snares slightly late — a hair behind where the metronome puts beat 2 and beat 4. The hi-hat stays on the click; only the snare drags. Not millisecond-late: perceptibly late, like an actor pausing before the punchline. This is the entire boom-bap sound.