This is the bass drum exercise from Mark Guiliana's book that I had attempted to record yesterday. It starts sounding vaguely as it should. It is done twice, once in 8th notes, then in triplets. The hi-hat marks all beats, and the snare/bass drum alternate. One strokes on the snare, one on the bass drums. Then two strokes on the snare, one on the drum. Then three strokes on the snare, one on the drum. When the number of strokes on the snare drum is even (not a multiple of 3 minus 1), the second figure is shifted with regard to the beat, and this poses coordination problems.