What it is
The campana is a hand bell the bongocero switches to in the montuno, the most energetic part of a song. It's held in one hand and struck with a stick.
When it comes in, the music gets louder and denser: that's the sign the montuno has started.
The strokes
Mouth: a stroke on the wide end, loud and open. Neck: a stroke near the narrow end, short and dull.
The rhythm is simple: the mouth on 1 and 3 (5 and 7), the neck on 2 and 4 (6 and 8) — a stroke on every count.
What a dancer hears
The bongo bell strikes evenly on every count — the clearest metronome in the band. The loud mouth strokes fall on 1, 3, 5 and 7.
Lost? Hold on to the bell: "1" is a loud stroke followed by a quiet one.