Any Yamaha GH1, GA1, or GP1 that I resell gets the bottom 6 notes above the tenor rescaled. It's a quick easy repair. Actually, Yamaha had made this switch already on later versions of the GH1, so if your client has one with wound strings in the tenor then he's probably fine.
I replace the strings with wound bichords, but I know some techs replace them with Paulello wire.
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Peter Stevenson RPT
P.S. Piano Service
Prince George BC
(250) 562-5358
ps@pspianos.com------------------------------