First of all, welcome to everyone on my first post to this forum.

I have a M&H Model A, from 1935. I'd like to know more about the different scales that have been / are produced for the A. As you're probably aware, the scale design is identified on the far bass side of the scale, e.g. A5, A9. I've got an A9. My understanding is that the As typically are A5, or maybe A4, that there are scale designs from A1 to A11, and that the A9 was used for the Model A version with the player piano.

Now, my general request is for more information, and specifically, for a discussion on how these scales designs differ, technically and acoustically. That includes bridge design, with resultant consequences for hammer voicing.