Getting the most out of an inexpensive chromatic button accordion

Bought a chromatic button accordion and fixed some things.
Contents:
1:00 - Description of the accordion
4:10 - Removing the fifth of the dominant seventh chords
11:04 - Adding an extra bass register
17:02 - Improving the treble-bass balance
(NOTE: Regarding the loosening of the reed blocks to improve resonance (22:30), I now have my doubts about this and have tightened them quite firmly. I now think this is better since the vibrations travel more easily through the material when it is tightened. Apologies for the dissemination of fake news, and I still don't know what's fake and what's real!)

Technical details of the accordion:
Barcarole Professional
Treble:
5 rows, 83 buttons (6 dummy buttons)
46 notes (C - a`` on lowest register)
4 voices: 16-8-8-4
11 registers
Bass:
120 buttons
4 voices:
1: G, - F#
2: G - f#
3: d - c#` (chords)
4: d` - c#`` (chords)
3(4) registers: 3+4, 1+2+3+4, 2+3 (after fix, also 1+2+3)
Note: dominant 7th chords consist of all 4 notes (after fix, only 3, without the fifth)

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