<HTML>In a message dated 12/3/01 6:07:48 PM Central Standard Time, gmcc@charter.net (Gary Mc) writes: <BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">How do I know if I'm tuning a 2:1, 4:2, or 6:3 octave? And why are they used in different places.  How do I know when to use which one? Sorry to be so elementary, but I know the terms and what they mean.  I just don't know when to use one in place of another. (I may know this, but I just don't know if I know it!) Thanks for any advice Gary McCormic</BLOCKQUOTE>k This is a very good question.  You won't find any information about it in most tuning books.  The reason is that this knowledge was not very well known until fairly recently and is still not well understood by many technicians.  The advice given to get the book by Rick Baldassin RPT, "On Pitch" and the PTG study materials is your best opportunity to learn and understand this fine point in tuning. Please understand that distinctions in octave types represent the highest level of refinement in tuning.  Therefore, if you feel you are at a more elementary stage, there are other things which are more important to understand first.  It is true that various octave types find themselves naturally from experienced aural tuners who may not even understand the concept.  Appropriate octave types are also a part of the usual electronic tuning programs offered by modern Electronic Tuning Devices (ETD). Inharmonicity is the fundamental reason behind the existence of differing octave types.  Any person who tunes pianos must understand the concept of *inharmonicity*.  (You may not find the word in a regular dictionary).  Every piano string has not just one frequency but a whole spectrum of frequencies, each one known as a *partial* (or in usual laymen's terms, a *harmonic*). The frequency we think of and generally focus upon is called the *fundamental*.  Because of the *stiffness* characteristic of piano wire, each of the higher *partial* frequencies is higher or *sharp* to the fundamental.  They are always *greater* than a theoretical multiple such as 2, 2.5, 3, 3.25, etc.  The higher in the spectrum of partials, the more *distortion* there is, in geometric proportions. The amount of *distortion* is the essence of the complex puzzle there is to solve in order to really achieve a truly fine and artful tuning. To begin tuning aurally, a single octave must be created.  The A4 having been tuned, the note A3 must be tuned.  Rather than simply tuning an octave that "sounds good" or seems to have no beating, it must be kept in mind that to reconcile the tuning of the entire piano, the initial and central octaves should be stretched as much as possible to blend with and accommodate the outer octaves where making a match with the central octaves will be a much more difficult task. So, this first octave should be made to be on the wide-of-perfect side with a very slow beat (about 1/2 beat per second).  When tuning Equal Temperament (ET) the best and usual compromise has been found to lie *between* a 4:2 and 6:3 type octave.  On pianos with relatively low inharmonicity, there is not much distinction.  On others, with higher inharmonicity, the difference can easily be heard by a skilled technician. To determine these distinctions aurally, there are tests.  Many in the tuning profession do not know these tests.  Many find it hard to understand how using a note which *has not yet been tuned* can serve as something to use in a *test*.  If this is a question for you and a description of how to use these interval tests is what you'd like to read, please ask.  I surely can explain them, I wonder what other kinds of answers you may get. Bill Bremmer RPT Madison, Wisconsin <A HREF="http://www.billbremmer.com/">Click here: -=w w w . b i l l b r e m m e r . c o m =-</A> </HTML>