Ah, the mysteries. Generally speaking, the 4:2 is preferred in the middle of the piano at about F3 up into the 5th octave. The reasons are: The fourth and second partials tend to be strong in this range and to beat unnicely if not closely matched. Likewise for the 6:3 from about E3 down into the bass (farther on small pianos, changing to 8:4 and even 10:5 on big pianos, i.e., long bass strings and big soundboards. There are no hard and fast rules applying to all pianos! In many (most) cases, your temperament octaves must be slightly (SLIGHTLY) wide to make a good temperament. Widening the 4:2 starts to infringe on the 6:3 width ... The octave tests give you some information that will help you determine two things, purity/width of the octave, i.e., beat rate, if any, and that your octave is pure or wide (it must never be narrow). Use the 3rd-10th test on the 4:2. If tuning the top note, say F4 to your F3, tune it pure then a noodge more wide. The beat rate difference should be no more than the beat of a durn clean fifth, i.e., 1/2 bps or less. While learning, it can help to test your octaves with ghosting: In our example silently hold down F3 and F4 and whack the 4:2 key, i.e., F5. You should hear something between pure and a very slow roll. If you are unsure that your octave is wide, tune a 4th or 5th inside it. In the F3-F4 example, tune either A#3 or C4. Use the 3rd-6th test on the 4th and the 6th-10th test on the corresponding fifth. You MUST end up with a wide fourth (6th faster than 3rd) AND a narrow fifth (6th faster than tenth). If you have a nice, quiet octave, a 4th beating 1 bps or so and a very lazy fifth, then you have three notes that are tuned purty accurately--in relation to each other, that is. 6:3 octave, use the m3rd-M6th test. If they beat exactly the same, you have an exact 6:3 octave. The reference note for ghosting is one octave + a fifth above the higher note of your octave. This is the 6th partial of the lower note and 3rd partial of the upper note. Remember that the minor 3rd is a narrow interval so, for example, if the octave is too narrow, the m3rd will beat faster than the M6th and vice-versa if it is too wide. There is so much more, including using the m3rd-M6th test for a stretched 4:2, that we are only just beginning. Treble tuning ... someone else, please. The 2:1 is not that tough and is required for octave 7 of the tuning test, but between the 4:2 mid-range and the last octave (or to the top in the real world, if it sounds right, you should be looking for 4:1 double octaves which are, among other things, good candidates for ghosting, at lease up through the fifth octave. Here you will need to learn the 10th-17th test and the 3rd-17th test. Mostly to ensure that the octaves are a little wide, never narrow, then sound quality and double octaves will help you nail the 4:1. S'Late, bye ... Alan Barnard Salem, MO Original message From: "Matthew Todd" To: pianotech at ptg.org Received: 8/21/2007 10:11:26 PM Subject: 2:1, 4:2, 6:3 octaves I have been really, really studying tonight. Can someone please explain the system they use to tune 2:1, 4:2 and 6:3 octaves. I am so close to grasping this concept, but I think I need another tech to explain it to me besides Reblitz. In the octave interval, if I were to tune a 4:2, the fourth partial of the lower note theoretically has the same frequency as the 2nd partial of the upper note. Do those partials normally dominate each octave? How can I tell whether to tune a 4:2 or a 6:3? Oh, and lets leave inharmonicity for another post. I am just trying to grasp this main theoretical concept. Thank you! Matthew Need a vacation? Get great deals to amazing places on Yahoo! Travel. -------------- next part -------------- An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/20070821/76414b84/attachment.html
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