However I have a general problem with the abc code: the "key treble-8" is not completely implemented. It does not implement the -8.
So you needed for voice 2 the %%midi transpose -12 statement, which is odd.
In case the abc code is perfectly implemented it would be of great help for the transformation from old violin key's like alto2, alto3 and alto4 into treble. Nowadays you have to go to a tool that tranforms your pitches one octave, copy past parts of the scores, in order to get a good pdf score file that can be used by musicians.