vb.mus is set to loop to _B2 on line 25, but I am fairly certain it should loop to _B3.
Reasoning:
_B1 and _B2 form a pair of motifs that are clearly mimicked by _H1 and _H2. _H2 followed by _B2 is synonymous to playing either of them twice, creating a duplicate motif.
The beginning of the waveforms for _H2 and _B2 have artifacts tying them to their predecessors, which become jarring when played after themselves.
Changing the loop to _B3 creates a smooth loop.