I think Michael has pointed out that there is more to clean treble sound than just the shape of the capo bar. I too have had pianos that continued to zing after a "proper" shaping, even after string leveling, reshaping, and checking string deflection angles. I suspect capo bar smoothness is very important, but other factors include updraft angle, string tension, length of front duplex wire and diameter of wire, hammer hardness, as well as profile of the capo. Like Ron, I too have had the experience of eliminating string noise in the capo section by resorting to hammer voicing after all capo remedies failed. I felt like I was treating the symptoms instead of the problem by needling the hammers, since I could stop the noise by touching the front duplex section with a finger. However, some deep shoulder needling stopped it without appreciably changing the tone.
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