QUOTE (gcarr @ Jul 15 2008, 02:44 PM)

I have now to find a top range 46 button MacCann (the only standard size one), and ask a good concertina repairer to add low notes, and take out upper ones on right hand side.
I think the reality is that to get a worthwhile concertina out of this, you need new reed pans and new actions, so that you wouldn't actually use enough of the original 46-key to make it worthwhile cutting up. And you'd probably want a consistent set of reeds, which means it would be better to cannibalise a 48-Crane rather than a 46-Maccann.
If you used the existing reed pans, the insoluble problem is probably that you won't be able to design lever runs for new low reeds placed where the high reeds used to be. The same problem exists, either if you put in a new lower row of buttons (seeking to use the existing lever runs for the retained reeds, but probably putting the new buttons in an uncomfortable place), or if you use the existing button locations and re-assign them all a row up (requiring new lever runs for every reed). The other, less insoluble, problem is that the existing cutouts for high reeds are too close together to be sufficiently enlarged for the larger reed slots and larger chambers you will need. You could cut out and replace part of the reed pan with a new piece of wood, or else fill all the holes and slots in and cut new ones in new locations. I don't think that a concertina with a reed pan that had been so modified would really be a high quality concertina any more.
If you "fixed" the RH, then, in my opinion, the shortcomings of the LH would now become overwhelming, and you'd have to "fix" that too. Your lowest C#, D and D# would all be in the overlap. I think that would make it a very difficult instrument to make effective use of, as a duet. This is related to "the worst problem" on a 46-key Maccann, that most 46-Maccann players already complain about, which is the lack of a low D in the LH. With your lower RH, I think you would feel its absence, and its neighbours' absence, even more strongly. I think every one of us would give the LH high C or G# for the low D. But replacing even one high reed with a low reed is not practical to achieve within what a "repairer" can do: it would require major redesign. So I don't think it has ever been done. So, in practice, to get a useful concertina, you really need a new LH reed pan and action too, and probably a different set of reeds, perhaps scavenged from a 48-Crane.
A year or so ago, someone was selling a Dipper-modified Maccann with some additional LH low reeds put on to it. But it did not involve replacing any of the existing high end reeds. One reed was a replacement for an existing reed, but it was a low end reed so that the space was enough for it, and it was in a suitable location to get a suitable lever run. The other reeds were fitted into existing unused space in the centre, which is a place possible to design lever runs for. And this was originally a 57-key, so that there was significant unused space in the centre to use.
Basically, if you want a RH down to a Middle C on the RH on a duet of 48 keys or fewer, without designing an entirely new concertina, then you have to play Crane or Hayden.
The other "solution", which is what many 46-key Maccann players do in the real world, is to treat their instrument as a piccolo, and play an octave above the written pitch.