[Lowboy]

Alan is the expert, but I would add that just because a melodica has holes or slots on the back, does not mean the sound is projected from these holes or slots. Often the holes or slots on the back are there for what I imagine is air circulation, sound tuning (with most of the sound emerging from beneath the keyboard), or esthetics. Covering the slots on the back of most melodicas will have minimal effect on the tone. Lowboy