If I have a sequence like this
MIDI.setVolume(0, 120, 0);
MIDI.noteOn(0,50,127,0);
MIDI.setVolume(0, 50, 1);
MIDI.noteOn(0,50,127,1);
MIDI.setVolume(0, 25, 2);
MIDI.noteOn(0,50,127,2);
I expect that each note would be quieter than the last. Instead, all three notes are of the same volume.
This might also be the responsible for the lack of a fadeout in MIDIs with type 7 controller events, like this one