I would look at it from a different direction. If you make the standard construction such that the different button-containing end plates can be constructed independently and simply attached into/onto an unvarying "core", then
- If someone wants a Hayden, attach the Hayden ends and ship it. If someone wants an English, attach the English ends and ship it. Etc.
- And if someone wants two or more layouts, all that's necessary is to include each set of ends.
That is exactly what I meant by "in form of detachable electronic keyboards". Furthermore, you don't have to make whole endplates or drill holes in pre-cast ones (casting isn't realy an option, as it requires large runs to be economicaly efficient) - you can just design an endplate with replaceable insert. Apart from englishes, all (?) other systems use handstrap/handrest construction and only Dipper custom uses long three rows layout, so they would all fit in some well defined area.
I believe Colin's franglo uses both bar-strap and thumb loop, and the Wheatstone "double" uses thumb loops like the English (but no plates for the little finger), but presumably something like that would be special order and cost extra. As for that "well defined area", though, it would presumably have to be wide enough for a reasonable Hayden keyboard with enharmonics (more than 7 buttons?) yet "tall" enough for a decent Crane (7 buttons?) or even English (8 or 9 buttons?) layout.
But you could also have more than one standard size... in particular, a smaller size for layouts with fewer buttons (30 button anglo?), which would simply not use all the code assignments included in the larger array.
As to making instruments symetrical in terms of button number: for technical reasons I'm assuming a 64 button "poll" to divide. With 64 button duets you will want (at least I would) to have a slightly more buttons on the right hand side.
I'm curious about your "technical reasons" for this 64-button limit. Why not, e.g., 128? (A single byte, after all, supports 256 different codes. However, I've never tried to program MIDI, so I don't know whether its format limits you.) That would allow for even more than Brian's suggestion of 65 buttons, plus numerous control codes, and even allow some redundancy or unused codes (like our DNA?). Come to think of it, they make 88-key MIDI "piano" keyboards with added controls. And the keyboard I'm typing at right now, while not MIDI, has 113 keys. So I wonder, why impose a 64-button limit?
As for wanting more buttons on the right hand side, I wonder what sorts of arrangements you have in mind and what sorts you're excluding. I might note that many piano arrangements have a greater span in the left hand than in the right, and not just through octave duplication in the bass. My impression is that current duet players tend to go for instruments with more buttons not so much to get extra range at the top but to get extra range at the bottom... and to get more overlap.
That defines a split of the poll between sides, wich is then fixed for any other keyboard, as some wires must go through the bellows and this cannot be overcome by interchangeable endplates inserts.
Why must wires go through the bellows? I'm typing at a wireless keyboard. I believe it uses radio frequencies, but infrared or even visible laser light (which wouldn't be visible outside the bellows) should work just as well. It has been suggested that connection to a synthesizer and/or mixer/amplifier/speakers could be wireless. If that's done, then why not use it also for communication between two ends?
Apart from that, any layout could use this poll to the maximum of (example split) 30 buttons left, 34 buttons right.
Ah, that unequal split again. Unequal split isn't the best fit for an English (or Linton) layout.
One thought though: with MIDI, if the instrument is built as single chanel only, there is less point for large overlap as you won't get more sound from playing same note on two buttons… And many DAV programs don't support multiple channel MIDI recording.
What's DAV? (Wikipedia gave me many possibilities, but none of them seemed to fit this context.)
I'm certain that the main reason for the overlap is not to get more volume on particular notes by playing them on both ends simultaneously but to enhance playing through alternate fingerings, either to avoid or to take advantage of parts crossing between the hands, depending on the circumstance. More overlap is desirable because it provides more options for musical control.
Edited by JimLucas, 19 March 2014 - 02:50 AM.