The bass tumbao — the salsa bassist's pattern, here from Levine's fig. 20-26 where it is written for the pianist's left hand as an exercise (Scivales Ex-116-1 is the same shape on G). Two notes per bar: the fifth on the and-of-2 and the root on beat 4, held across the bar line. Most tumbaos accent beat 4, reinforcing the conga's open tones; beat 1 is empty except in the very first bar of a tune (dropped here so the loop stays honest).
Listen for the "bombo–ponche" shape: the pickup on the and-of-2 and the long note on 4. The bass sounds like it is a beat early all the time — that is the point. Against the piano's montuno (Levine's single-note C figure) the only shared attack is the and-of-2.
How it sits on the clave: the beat-4 note lines up with the last stroke of the three side; the and-of-2 with its middle stroke.
Practice: Levine's exercise — montuno in the right hand, tumbao in the left — is hard and worth it; it is how you learn to lock with a bass player rather than fight one.