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Converting an existing guitar to just or pure intonation

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Converting an existing guitar to just or pure intonation

Postby Ken Whisler » Tue May 17, 2016 11:01 pm

A friend of mine has asked if I could convert an existing guitar's fretboard to just or pure intonation for his own use in plain and Gregorian chant. He is a priest in an urban parish in a blighted neighborhood, so this will be a freebie.

I remember listening to John Schneider's Lou Harrison album back in the 90's, and there is a pic of the Mattingly guitar used with interchangeable fretboards. These western ears could never get used to the intonation, but my mind could change in a chant setting.

Questions are:

1) Where can I find templates or calculations to measure out the frets?

2) Presuming the initial try will be down and dirty on a cheap instrument; removing frets and filling the existing slots with epoxy and the cutting new slots, how should I cut the slots? My own method for the past several years is as Paul Jacobson explained it to me: cutting the slots> widening the slots with dental bits in a Dremel w/router base> then gluing the frets in with epoxy. The partial frets would rule out cutting the whole slot, and I'm afraid the Dremel with a dental bit is not strong enough to actually cut the slot.

Any thoughts are appreciated.
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Re: Converting an existing guitar to just or pure intonation

Postby Brad Heinzen » Tue May 17, 2016 11:26 pm

I think you'd have to pick a key, and even then, you couldn't have continuous, single frets at each location. Our standard frets only line up at each string because of equal temperament (more or less!).
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Re: Converting an existing guitar to just or pure intonation

Postby Doug Shaker » Wed May 18, 2016 1:14 am

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Re: Converting an existing guitar to just or pure intonation

Postby David Collins » Wed May 18, 2016 9:02 am

Yup, you'll need to pick a key and tuning first, and unless each strong is tuned to the same note, you'll need offset frets. Beyond that, the calculations will just have to be whole ratios (plenty of resources online to find natural tuning ratios.

This will be a labor of love, and I would advise doing to an instrument that you can afford to mess up. In practical terms, I would suggest to your friend that a lap dulcimer may be much more appropriate for this application. Root - 5th - octave tuning, five whole step and two half step intervals (not much need to worry about a full chromatic scale for this use). A lot of old dulcimers are actually already spaced closer to natural than equal tempered, so you may be able to find one that doesn't need much modification.

http://youtu.be/ERF1Kk5kcR8
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Re: Converting an existing guitar to just or pure intonation

Postby Brian Evans » Wed May 18, 2016 10:18 am

I might make a flat fretboard, slice it into six tapered strips so I had one skinny fretboard for each string, slot and fret each strip for frets in the spacing you decide for the key you are going to put it in, reassemble the fretboard gluing the strips back together is some kind of jig to keep it all level and square. I would probably do most of the fret dressing before I glued it back together so I just had a light level to do after it was all put together and on the neck. Before I did that I would point out the natural just intonation of a lap dobro or lap steel if you tune it that way and only play in one key ( and never play other chords than the I chord I guess). It would be less work to make a lap steel from scratch than to make a just intonated fret board.
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Re: Converting an existing guitar to just or pure intonation

Postby Jim McConkey » Wed May 18, 2016 6:01 pm

If you want to try it out cheap, how about just putting on a fretless finger board with no slots and using tied gut frets, a la early violas da gamba?
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Re: Converting an existing guitar to just or pure intonation

Postby Clay Schaeffer » Wed May 18, 2016 9:28 pm

Or combine Jim and David's ideas and make a tied fret stick dulcimer (strumstick).
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Re: Converting an existing guitar to just or pure intonation

Postby Stephen Neal Saqui » Wed May 18, 2016 10:32 pm

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Re: Converting an existing guitar to just or pure intonation

Postby Alan Carruth » Thu May 19, 2016 12:26 pm

Tied frets won't work, since they can't make the necessary 'kinked' pattern. That's one of the things that pushed the use of Equal Temperament: the lute and gamba players couldn't play in tune with the keyboards set up for mean tone or just scales, let alone the fretless fiddles and singers. There's just no easy way to do this. Probably the simplest thing would be to use 'staple' frets, as was done sometimes on early mountain dulcimers. They used baling wire, but you could get brass rod stock and bend it to shape. Predrill holes to make sure it's located properly.
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Re: Converting an existing guitar to just or pure intonation

Postby Clay Schaeffer » Fri May 20, 2016 7:00 pm

Tied frets could work for a stick dulcimer, with the fifth always used as a drone or tuned D d dd (or a variation there of) The advantage to the tied fret would be the ability to change from one key to another (between songs) but still keep things "justly" tuned.
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Re: Converting an existing guitar to just or pure intonation

Postby Hans Bezemer » Sat May 21, 2016 3:46 am

If being able to play in different keys is an issue, you could consider to use a 31-tone divisions of the octave.
This will give a meantone kind of tuning, so somewhere in between 12- tet and just tuning.
There's an excellent article on Wikipedia about 31-tet.
There is a Dutch guitarist who uses a 31-tone guitar with partial frets.
Searching YouTube on 31-tet music / 31-tet guitar will gives some hits.
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Re: Converting an existing guitar to just or pure intonation

Postby Ken Whisler » Sat May 21, 2016 9:44 pm

Thanks to all for the responses. I will digest it all and report back on the results....someday. ;-)
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Re: Converting an existing guitar to just or pure intonation

Postby Mark Day » Mon Jul 18, 2016 10:51 pm

Paul Beier, a lutenist, and apparently a software developer, wrote a string and fret calculator that can calculate fret positions for several temperaments. Google "Beier String and Fret Calculator" and you'll find a few places where you can download it for free. I have used it in the past and it worked fine.
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Re: Converting an existing guitar to just or pure intonation

Postby Albert Stacy » Wed Jul 20, 2016 8:22 am

Why not you ask your friend for exact measurement as he will better guide you that how your convert your guitar.
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