Sort:  

The air comes out of one hole and the block forces the air back into the other hole making the sound. This one is low d sounds.

He does a good job with drilling out the holes and the tunning.

Coin Marketplace

STEEM 0.14
TRX 0.24
JST 0.034
BTC 97009.53
ETH 1840.91
USDT 1.00
SBD 0.81