majalan

Copperbox revision 3046.

Work on Event concatenation, which is more subtle than I had anticipated.

One principle is that an Event should only generate one impulse regardless of how many sub-events it is made of. This means avoiding Monoid's mconcat and instead only taking the leftmost answer.

Another issue is that horizontal concatenation (for trills, tremolos, ...) should probably not use the timespan of the left event to place subsequent events. Timespan suffers from the already recognized problem that it doesn't represent staccato and legato / sostenuto notes.