Hi Alan, > like a heavenly choir. I had always suspected that it changed the harmonic > content i.e. changed the relative amplitudes of the upper partials. I > experimented once to find out what was going on and recorded the before and > after effect into an FFT analyzer. To my astonishment, it was not the > partials that increased in volume relative to the fundamental, but the > fundamental had increased in volume relative to the harmonics. The mandolin > rail appears to have the opposite effect. The softer the hammer surface, the lesser higher frequency energy in the impusle (the hammer's "whack" against the string), the less higher harmonic energy in the response (the ringing of the string). When the UC is engaged, the hammer strikes the string with less pounded/flattened/hardened felt, hence less higher-frequency energy. Yes, I realize the strings still supposedly line up along the same positions on the hammer (just shifted), but I doubt it's *that* exact. Related question: Do hammers harden faster when people don't use the UC? I'm thinking that the occasional shifting of the hammers may help to keep the felt "fluffed," so to speak. I notice my hammers become somewhat softer after a bit of Hannon with a half-engaged UC. (It doesn't last for long, though.) Peace, Sarah
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