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