We have seen attempts in at this before... the 5 voice Hohner Morino (M, N, S) accordions only let you choose between M and MMM, so no MM possible. WIth the M there is nothing you can do about it (besides permanently disabling the 5th voice by taping it shut)). On the N and S it is theoretically possible to change the registers and operate the M+ and M- independently.
I have added a slider for the M- on the Morino V S.
The first pic shows what it looks like.
The second pic shows whats on the back off the grille.
The third pic shows the disconnection between the regular register slide and the connector to the register slides inside.
Works very well. There is enough friction to not need any blocking mechanism (for on or off).
When playing on is up and off is down, so there is no danger of the tremolo becoming engaged all by itself (due to gravity).
I have added a slider for the M- on the Morino V S.
The first pic shows what it looks like.
The second pic shows whats on the back off the grille.
The third pic shows the disconnection between the regular register slide and the connector to the register slides inside.
Works very well. There is enough friction to not need any blocking mechanism (for on or off).
When playing on is up and off is down, so there is no danger of the tremolo becoming engaged all by itself (due to gravity).