Plena is Puerto Rico's sung newspaper — born in the barrios of Ponce around 1900, a call-and-response song about whatever just happened, carried on frame drums (panderetas) and easy to play walking down the street.
How it sits: felt in two, no clave. Three panderetas interlock: the seguidor (low, conga-lo) plays both beats of every bar, the second one heavier; the punteador (conga-hi) fills the offbeats with a sixteenth pickup into each downbeat; the requinto (rim) is the improviser — here one fixed fill in bars 3–4. The güiro (shaker) scrapes long–short–short on every beat. Guitar or cuatro strums the one, two-and figure, and the bass walks root–fifth on the beats through C and G7.
Listen for the punteador's sixteenth pickup: it gives plena its forward tumble.
Practice: play seguidor with your foot and punteador with your hands, then try inventing your own requinto fills in bars 3–4.