Hello Gianluca, I did not gap the melodica since the only issue was the air leak. Once I replaced the bladder all worked fine. As I have mentioned in the past post, the three bass melodicas have the same issue. If you blow just a little to hard you will choke the reed or not enough and the reed won’t sound. I bought the Suzuki and the Hammond brand new and they both came with the same issue. The fastest Bass melodica is the Hohner Basso by far.