"Ran Kan Kan" or "Mambo Gozon" by Tito Puente illustrate the mambo bass. The bass is always playing the tonic note of the next measure, on the 4th beat of the measure that precedes it. The 2 songs I mentioned stay on one chord, so the bass is always playing tonic, fifth to tonic. The fifth is played on either the upbeat of the second beat, or on the third beat. The tonic is always on 4.