Susan writes: << Take out the last mute, and see what happens to the unison and its timbre, when played normally. Often it starts to sound crummy. Pluck the fourth string to be sure it isn't out in left field, and then move it a very short distance up and down, until the unison rings sweetly again. The timbre of the unison determines where the fourth string is tuned, not its exact pitch, but it should be close to the others. << Greetings, I have found that the Bluther's extra string gives me the best results when it is tuned just slightly flatter than the unison. I think it is because of the phase interaction, operating through the Weinreich-described coupling at the bridge, produces more sustain. When the frequency of the impelling force (the unison) is lower than the resonant period of the structure upon which it is acting, (the fourth string), the two will always be in phase. If the impelling frequency is higher, the two will be out of phase. It is this out of phase arrangement that augments sustain. Think of pushing a swing; if the swing takes 5 seconds to go out and return, and you give it a push every 5.1 seconds, you will always be helping it go away from you. If you push it ever 4.9 seconds, you will be resisting it every cycle. By creating this micro-resistance between the unison and the sympathetic fourth string, I believe that it takes longer for the unison's energy to pass through the bridge, thus more sustain. If I tune the fourth string higher, the tone seems to be more brilliant or louder, but of shorter duration. Just a thought, Regards, Ed Foote
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