- 15:50) Video lessons: https://www.youtube.com/watch?v=mmd_7p62Z18 (by de Miranda Score (Or PDF. BSD: Back surdos (L for low, H for high R/L: Accented Note (right/left hand suggested r/l Quieter, unaccented note * A trill, generally three very fast notes on repique/caixa, two or three for surdos