I just had that same problem on an SD 6. I looked for the paper clip on the board, tightened plate screws (which helped the sound) and scratched my head and tightened every screw. Mid range sounded awful. I mated hammers to string, seated strings, etc. It was the sostenuto rod clips. Them things were rattlin to beat all get out. Should have been the first thing I tightened, they are right out front, highly visible....... Sigh Keith
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