These class-based attributes use data.MIDIVALUE_PAN
att.midiInstrument/@midi.panSets the instrument’s position in a stereo field. Values of 0 and
1 both pan left, 127 and 128o both pan right, and 63 and 64o both pan to the center.
Positive percentage values pan to the right, negative ones to the left, and 0% pans
to the center.