Yambú is the oldest and slowest of the three urban rumbas — a couple's dance in the Havana and Matanzas solares, played at first on wooden boxes (cajones) before congas took over. Unlike guaguancó, the man never makes the vacunao pass; the dance is courtly and unhurried.
How it sits: the clave layer is the rumba clave, 3-2. The palitos (sticks on a catá or the side of a drum, on rim) play the cáscara-shaped line that also drives guaguancó. The conga-hi is the tres-dos / segundo, the conga-lo the salidor: two open tones early in the 3-side, then the low drum answers at the end of each half of the clave, closing on beat 4 of the 2-side.
Listen for how much space there is: at this tempo the palitos carry the time and every drum tone is a statement.
Practice: play the palitos with one hand and the clave with the other before adding the drums; then speed it up and you are most of the way to guaguancó.