In a message dated 11/6/98 12:50:32 AM Central Standard Time, pianotoo@imap2.asu.edu writes: << > List, > "Even the unison strings of a piano sound better when de-tuned to a minute > degree (app. 2 cents total spread, corresponding to 2/3 beat per second @ > a440). Fortunately a good piano tuner attempting to achieve true unison gets, > on the average, a similar result" > > Dr Daniel W. Martin > H D Baldwin Co > Tech Jo. April 1964 >> The figure above is twice outside the tolerance on the PTG RPT Tuning exam. I think most contemporary tuners would consider those to be poor unisons. Someone else mentioned a possible error in figures. Could the author have meant .2¢ (not 2¢)? If so, the variation from exactly on would be in line with what I have seen come from the best tuners who have taken the Exam and whose unisons have been measured in that clinical setting. There was a story in Scientific American about 20 years ago called "The Coupled Motion of Strings". Not having the text for reference, I remember that it concluded more or less that the best tuners produce this kind of error. My personal opinion is that the tuner strives for a perfect unison which means "no beat". If there is a 1/2 beat per second or less, the tuner may be satisfied with it because the beat is simply inaudible. I think it can matter depending on the circumstances. In a usual, in-home tuning that I do on a piano say, once a year, I won't listen to a unison long enough to even know if there is that slow of a beat. During a concert tuning however, I may pound away at a unison for a considerable time, just to make *sure* there is no hint of a beat. >From what I have learned, the unison is really the only interval where it is even possible to have absolute perfection and that is the goal. 5ths and octaves can *sound* pure and thus be perceived as beatless but we know from the understanding that has come about in recent years that inharmonicity prevents coincident partials from ever lining up perfectly. Therefore, there is always some kind of beat in these intervals whether it is perceptible or not. When tuning the 5th and the octave, the tuner may choose to favor one set of coincident partials over the other or may make a compromise between them in order to create a desired effect, expanded or contracted, as desired. With the unison however, I believe the consensus has it that it is to be absolutely pure or as close to that as possible. The very small variances that have been noted in the unisons of the best tuners are a result, I believe, of the physical limitations of both the piano and the tuner him/herself. An error of .1 or .2¢ is *readable* by an ETD but probably inaudible to the ear. Furthermore, there is always the dilemma of the False Beat. Practically no piano is completely without them. It is possible that some very skillful and artful tuners can in effect, cancel out a false beat by countering it with a deliberate but slight beat in the unison. In such a case, the three strings would most surely have as much as (or perhaps even a little more than) a full cent difference between them. Sincerely, Bill Bremmer RPT Madison, Wisconsin
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