DIGITAL GUITAR AUTO-TUNER PROJECT

I read in sci.electronics.design that Bob Monsen wrote (in ) about 'DIGITAL GUITAR AUTO-TUNER PROJECT', on Mon, 25 Apr 2005:

Look for a winding handle at about waist-level. (;-)

as

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hence

The number of points used for resolution can be independant of the duration of the music input signal and the sample rate. See comments in other comp.dsp threads about FFT interpolation and zero padding.

What makes you think I haven't? Depending on the circumstances (type of instrument, amount and type of background noise, microphone characteristics, cpu power available, preferred user interface, etc.) and metrics (cents accuracy, response time, etc.), methods using FFTs as part of an algorithm can be either better or worse than the method you describe later on in this thread.

-- Ron Nicholson rhn AT nicholson D o T c O m

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Classical guitars have a tilted bridge (bridge compensation), so in effect, all its frets are non horizontal.

So what if there were? Anyway, with all the cross posting, there bound to be some groups whose charters touch on every part, but probably none that touch on all.

Jerry

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That seems to suggest that good performance depends in part on a low-pass filter, and that the cut-off is higher than optimum for low instruments. That also suggests that an improved model might have a variable filter or a choice of fixed ones. It tales longer to count cycles in low notes, but I think that effect must be secondary.

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Jerry

An FFT is only a transform from one set of basis vectors to another. One need not make any assumptions about what happens outside the FFT sample window, particularly the assumption that the waveform will repeat when it doesn't. And there are several windowing methods to help deal with any transient artifacts which might be related to the ends of any data sample window.

-- Ron Nicholson rhn AT nicholson D o T c O m

That describes it quite well.

Jerry Avins wrote in news:brydnYP4-My62 snipped-for-privacy@rcn.net:

It

Sounds like fun! but I'd take the Steinway.

Al

THERE HAVE BEEN A LITTLE LESS THAN A HUNDRED REPLIES ON THIS THREAD BUT UNDOUBTLY, IT TOTALLY CLEAR THAT YOU'RE THE ONLY ASSHOLE HANGING AROUND WITH SERIOUS THINKERS. IF IT SO HAPPENED THAT ALL OF THE OTHERS RESPONDED THE WAY YOU DID, MAYBE I WOULD THINK I WAS BEING AN ASSHOLE.

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IM GETTING THINGS QUITE FAST NOW AND I CAN SAY THAT I CAN FINISH THE PROJECT ON TIME. THANKS FOR ALL THE GREAT MINDS WHO SHARED THEIR VIEWS AND EXPERTISE. SO IM KEEPING MY JOB, IM GETTING A LOT MORE LEARNING THAN EVER BEFORE AND I FOUND NEW GREAT FRIENDS ALL OVER THE WORLD.

AS FOR YOU, SAY SORRY TO YOUR MOTHER BECAUSE YOU JUST PROVED THAT SHE DEFINITELY FAILED TO RAISE YOU WELL...

I read in sci.electronics.design that Jerry Avins wrote (in ) about 'DIGITAL GUITAR AUTO-TUNER PROJECT', on Mon, 25 Apr 2005:

An ichthyology group should be added, so that tuna experts can participate.

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

That sounds fishy.

How many newts in the scale?

How many scales on a newt?

Ken

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.

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The converse of a statement proves nothing. ;-)

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.

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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