I wanted to jump in on this as it’s a subject I’ve been thinking of for a long time.
My dream melodica involves tuning, tuning, tuning.
I don’t think anyone has mentioned individual reeds, I think this would be preferable for tuning and maintenance.
Also it would allow the player to try different timbres by being able to switch out different sets of reeds in the same instrument steel for bronze etc. or even a mixes, steel in the low notes for clarity bronze in the upper register for warmth etc.
What I’d really like to see is a way to access tuning without disassembling the entire instrument!
(A process I’ve found to be so frustrating and unrewarding I’ve all but given up playing the things.)
A harmonica can be tuned by only removing the cover. Likewise a reed organ(I’m not familiar with accordion maintenance) the advantage being you can immediately check your progress and the act of assembly/disassembly doesn’t affect the results.
This would probably require a re-imaging of the fundamental functioning of the instrument as far as how air flows?
Another feature not mentioned is key size. I find most of the current instruments keys to be a little cramped. As they are marketed for children to play the spacing and size make sense. The slightly wider spacing on the Piano 36 make a world of difference for my big adult fingers.
I know there is some discussion of sticking to the essential sound but since the effects subject was floating around I wanted to throw my two ideas in. For the wah effect I suggest a mechanism I’m familiar with from pump organ designs. I’m thinking of sound holes covered by a spring mounted lid that can be opened by a trigger mechanism. This would create a similar effect to Lowboy’s pressing against the chest technique.
For note bending: it’s been discussed before that placing the meaty bit of your thumb under the end of a white key blocking it from opening all the way will produce a bent note.
What I am envisioning is a spring mounted bar that when depressed would slide under the entire keybed and block all keys from depressing fully. In this way full chords, octave etc. could be bent simultaneously.