[Bruno Travi]

The advantage of the Clavietta with other melodicas, it can produce sound even when completely disassembled, blowing directly by each circular holes.
When I blow by one that correspond 5 smaller reeds and pressing the hole back I hear a sound change.

I believe that these 5 holes help to release pressure and avoid damaging ONLY the 5 smaller and more fragile reeds, so 5 holes are behind the 5 smaller reeds.