Claude,
This looks to me to just be an example of good old fashioned poor craftsmanship. If you look closely, no two mortise angles are the same, in fact one is nearly straight. This is pretty common and we see it here a lot, but mostly in the mortises on buttons. Pratt & Read had oscillating routers that cut all 88 of the front mortises and mortises in the buttons at the same time, and they had alignment problems to beat the band resulting in varying angles. There is no reason to offset the mortises in the front rail, just the balance rail when the key angles get too steep. Nice picture though, I've posted a few below as well. Mike
BLACKSTONE VALLEY PIANO
Michael A. Morvan
76 Sutton Street
Uxbridge, Ma 01569
(508) 278-9762
www.pianoandorgankeys.com
mike at pianoandorgankeys.com
www.thepianorebuilders.com
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