DIGITAL GUITAR AUTO-TUNER PROJECT

I haven't, but this did jog my memory - when I was a kid, we had a whole book (or maybe just a chapter of some book) of Lear's limericks. They were "family-friendly", as I remember. :-)

There was an old man with a beard, Who said, "It is just as I feared - Two owls and a wren, Four larks and a hen, Have all made their nests in my beard."

Cheers! Rich

--

Please change no_spam to a.lodwig when replying via email!

Tony (remove the "_" to reply by email)

I read in sci.electronics.design that Rich Grise wrote (in ) about 'OT DIGITAL GUITAR AUTO-TUNER PROJECT', on Tue, 26 Apr 2005:

Most of Lear's limericks don't have a punch line; the last line just repeats the first, so there are somewhat insipid. He wrote hundreds like that.

--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

How many newts in the scale?

--
  Keith

How many scales on a newt?

Ken

someinteresting reading about harmonics and overtones

harmonics overtones modes inhamonicity

The converse of a statement proves nothing. ;-)

--
  Keith

...

Oh? I thought it proved the converse.

Jerry

-- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

That's a good description that I omitted for brevity. You did a better job of describing it than I would have. The math, at least for two strings, is relatively simple. It is in many texts on diff-eq for engineers and physics lab demos as the "coupled pendulum" demonstration. Tuning the strings so that they just barely lock in frequency gives the longest sustain. If they slip just a bit further apart than that, the typical way-out-of-tune twang is the result. Just a touch with a quarter-inch-drive socket face up and turned with an Allen wrench can restore the lock. When three strings are involved, it is usually easy to identify the one that slipped. With two, even if you tweak the wrong string and so leave the note out of tune, it sounds so much better that you'll get laurels anyway. When you know how things work, the world is one big sandbox.

Jerry

--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

Ok, so my optical idea wasn't taken well. What about dopler radar? I remember when police radars were calibrated using tuning forks.

Yeah, microphones are just too obvious. ;-)

--
  Keith

No, I think you'll find that it does _not_ prove the converse. ;-)

--
  Keith

You mean that proving the converse doesn't prove anything? Oh, I get it!

The converse of something is nothing.

Proving the converse of something proves nothing.

Ah, so!

Jerry

--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

On Mon, 25 Apr 2005 15:43:53 -0400, Jerry Avins wrote:

Lower harmonics may well be locked together through the bridge interaction, though I believe that with increasing harmonic number there is less coupling at the bridge, the most coupling being at the fundamental. But there's another phenomenon in the piano having nothing to do with harmonics when several strings are sounded in unison, and this causes tje result described above, "Exact tuning makes the note loud ans it's [and its] decay rapid" and you would presumably see this in the amplitude on the oscilloscope, especially if you were looking for a perfect exponential decay of amplitude, and wonder what's going on. The decay will be quite fast in the first few seconds, then much slower in the seconds thereafter. When the hammer strikes the strings, they are all in phase, going up and down (presuming a grand piano with horizontal strings) together, and passing a lot of energy to the bridge (which goes up and down with the strings, and transferring this motion to the air), resulting in much energy being taken from the strings and a high decay rate. But due to the coupling at the bridge, one or two of the three strings will eventually change phase until one is going up while the other(s) are going down. At this point, much less energy (in relation to the amplitude of each string vibration) is transferred to the bridge (when one string goes up, its effect on the bridge is mostly canceled by the other string(s) going down, so the bridge moves up and down a lot less in relation to string motion), and since less energy is being taken out of the strings at the bridge, their decay rate is much longer. This is a part of the piano's sound (fast decay at the start of the note, slow decay after a few seconds) that cannot be made with a single-string-per-course instrument. I intentionally ignored the harmonics in the above description to simplify things, but the harmonics might also change phase in the same or a similar way. There have been three or four articles on the piano in Scientific American over the past 30 or 40 years, and I recall reading the above description of the string changing phase in one of them.

-----

That's funny! All the ideas are smart.

Just scroll down, folks, cause I don't top-post...

Have you tried this several times, with different guitars, or with the same guitar after changing strings? The fact that G is wirewound may have its effect, but there are other things. If the string does not have a very consistent weight along its length, perhaps one end is slightly thicker and heavier than toward the other (whether from wear, dirt accumulation, or faulty manufacture), the harmonics will be out of tune with the fundamental (or much moreso than with a 'good' string), and fretted notes are going to be sharper or flatter in relation to the open string than they will be for a consistent string. Imperfect strings are one thing that has driven me crazy (and I'm sure many other guitarists) before I figured it out. I read about "turning around the string" on a classical guitar in an attempt to get better intonation from it in Jose Oribe's book "The Fine Guitar" (I see it's now out of print, get a used copy before the price goes up any further).

You can tune for a particular key, but it makes things sound worse for different keys, or even some chords IN that key.

A piano is either tuned for equal temperament (I think virtually all of them are), or it only sounds good in some keys. I suspect both tuners aimed for and perhaps got equal temperment, but the second one knows more about how much to stretch-tune each instrument - the higher notes are tuned slightly sharp, and the lower ones are tuned slightly flat, relative to the middle octave. This is done so the higher notes are 'in tune' with the slightly-sharp harmonics of the lower notes. I've seen on the Web different tables of just how much to stretch-tune each of the notes on different models of pianos.

I do to, and it used to frustrate me as to why my guitars were out of tune and wouldn't tune right. Now I KNOW why. :) Actually, with some work and the proper tools (g-tune is a nice precision tuner for adjusting guitar harmonics (nut as well as bridge positioning) and general tuning) I've been getting things under control.

-----

I read in sci.electronics.design that Ben Bradley wrote (in ) about 'DIGITAL GUITAR AUTO-TUNER PROJECT', on Thu, 28 Apr 2005:

If one or both of the outer strings shifts phase, in such a way that the bridge can twist, the decay is different from the case where the middle string shifts (relatively).

--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
\'What is a Moebius strip?\'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

You can demonstrate this energy transfer with a really fun demo: Take three pieces of string, two weights (maybe a large hex nut, or fishing weight) - suspend one string horizontally, like in a door frame, or between two chairs. Make pendulums out of the other two pieces of string and weights, both the same length, and tie them at about 1/3 and 2/3 length on the horizontal string:

X---------+-----------+----------X X = support, + = knot | | | | - = horizontal string | | | = vertical string | | O O O = pendulum bob

Start _just one_ of these pendulums (pendula?) swinging, and watch what happens. See also

Activity 2.

Cheers! Rich

Ha! Another bit of usenet wisdom for my sig file!

-- Jim Thomas Principal Applications Engineer Bittware, Inc snipped-for-privacy@bittware.com

(603) 226-0404 x536 When you know how things work, the world is one big sandbox. - Avins