[MONOTONE] Note cut

[yesso]

I think the nicest feature in monotone would be note cut (after an 
arbitrary amount of frames), like SCx in ST3.  Since there is no volume, 
the length of the note would be the only available way to express the 
relative "importance" of a note.  Of course, this can already be done by 
setting the speed very high and having many unused rows between each 
note, but that's not nice for RAM consumption and is inconvenient for 
editing.