> > From: Ron Nossaman <rnossaman at cox.net> > Date: January 29, 2011 10:54:52 PM EST > > On 1/29/2011 9:05 PM, John Formsma wrote: > >> Someone on the list might have mentioned it. > > Not that I've seen. I don't recall anyone - ever, in any situation, mentioning testing unisons with intervals. This strikes me as weird, as obvious is it is after the fact. Maybe if I'd had some actual instruction at the start, it might have come up. I just sort of discovered the octave thing by myself. > .... > Ron N Hi Ron and John, I use 3rds and 6ths (and other intervals) frequently in tuning and testing unisons, though not exactly in the way John does, if I follow John correctly. I believe in a concept called "unison size," if I many coin a term (or perhaps someone has already coined it). As is standard knowledge, the various tests we all use rely on coincident partials, and unisons can be tuned and/or checked using similar tests. Here's how I do it: Let's say you want to tune or check a unison on note C#3, and let's assume for simplicity's sake that it happens to be a bichord. You could use A2 below it forming a major third as your test note. Start by muting off all but one string of A2, and all but one string of C#3. When you play A2 and C#3 together, the beating you hear is a coincident partial at C#5 (a 5:4 coincidence), and it is the 4th partial of C#3 that is participating in the beating. Listen to the beat rate, and then switch your mute to hear the other note of the C#3 unison. If you tune the second C#3 string so that the beat rate is exactly the same, or, if when you check the already-tuned other string the beat rate is exactly the same, then you have an exact 4:4 unison. If you used A#3 as your test note instead, the coincident partial is F5 (or, E#5, for us music theory nerds), and your coincidence is 5:4, with the 5th partial of C#3 participating in the beating. So, if you match the beat rates between the two strings of C#3 in this case, then you have tuned a 5:5 unison. If you use E3 as your test note, you have a 6:5 coincidence, with the 6th partial of C#3 participating, so you have a 6:6 unison, and so on.... --- If I read his post correctly, John is not referring to using mutes. If you don't use mutes and the unison is not good, then you will hear two (or three) competing beat rates at the coincident partial, and that blurriness in the sound (or lack of a clear beat rate at the coincidence, or really a shifting maze of phase reinforcement and cancellation) is your clue that the unison is not good. Thats why you don't like it. If you don't use mutes and the unison is good, then the beats at the coincidence will reinforce each other (be in phase), and will be nice and strong, which is your clue that the unison is good. Mmmmm good. So, really, the same principle of using coincident partials at a certain unison size by using a test note is at work with or without mutes. "Without mutes" is faster, of course, and "with mutes" gives you more feedback in correcting the wayward string (i.e. - it tells you if it is too high or too low, and by about how much as you compare the separate beat rates). --- I think that the "unison size" concept is most helpful in achieving consistent tuning in pianos with lots of mismatched bichords. By ear and using tests as outlined above, find the unison size that sounds the best to you (4:4? 5:5? 6:6? or even higher...), and then tune all of your mismatched bichords to that same unison size. The bass can be more consistent that way, even in those pianos with badly matched bichords. They may all sound "wrong," but they will sound "the same wrong." Sometimes consistency is the best you can do. As you choose the best sounding (least bad sounding?) unison size for the mismatched bichords on a particular piano, I suggest that you listen to the note by itself in evaluating the unison size, but then you should also listen to the note in the context of P8s, M10s and P12s above, and perhaps as the root of a major chord. Sometimes, the best sounding "solo" and "harmonic" choices for unison sizes can be different, and you will have to choose which to use. But, once you choose, I will once again suggest that you use unison size tests to tune the other problem bichords consistently. --- The "unison size" concept with mutes is also helpful many times with plain wire strings that are giving you trouble in pulling in a unison. It can even be used to tune high treble notes at more divergent coincidences, such as 5:1 or 6:1 (with the "1" being the high treble note; you are tuning a 1:1 unison, which is often the best choice in the high treble). At the very least, it gives you feedback about whether a certain coincidence matches or not. --- I would welcome other folk's ideas about unison size, such as: What unison size do you find works the best with mismatched bichords? What is more important, finding the unison size that sounds best solo or the unison size that works best in harmonic context? And the like.... Joe DeFazio Pittsburgh -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20110130/1161ccc1/attachment.htm>
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