DIGITAL GUITAR AUTO-TUNER PROJECT

Even though I have no idea what s.e.d. stands for, I doubt you can implement selectable intonation without getting into the firmware. In a YDP-233, one can chose among equal temperament (the default), or pure major, pure minor, Pythagorean, mean tone, Werkmeister, and Kirnberger, all with any base note. You can also transpose any number of half tones and pull the pitch of A440 in about .2 Hz increments from 427 to 453. It doesn't sound like the Steinway it replaced (my daughter has that now), but it's fun to play with as well as on. It will record two tracks and has a MIDI interface. More than I need.

Jerry

Re: inharmonicity in strings:

Yes, there is in fact a "lock-in" phenomenon that happens through the interaction at the bridge. But typical amounts of inharmonicity, at least in piano strings, exceeds the lock-in range. Inharmonicity is easily measured by precisely measuring the pitch of individual overtones and comparing them. Another way to verify inharmonicity is to observe the signal on a scope. If the overtones were all locked to the fundamental, the overall shape of the signal would be constant, just decaying in amplitude. Perhaps the individual overtones would decay at different rates. But it would be quite clear that the overtones are frequency locked. But that is not in fact what you will observe. If the scope is triggered by the fundamental, then the overtones will appear as higher-frequency components that are "riding to the left" as compared to the fundamental.

-Robert Scott Ypsilanti, Michigan

A piano's "stretch" over its 7.5 octaves is the better part of a semitone. By attaching discrete weights to the strings, most of the inharmonicity can be removed. (The windings on the low strings end well short of the bridges, reducing inharmonicity of the second partial.) A piano so doctored is tuned without stretch. It sounds awful!

Jerry

I agree. One point of quibble: even if the overtones were frequency locked, the wave shape would still change with time. Different overtones have different decay rates.

Jerry

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Winding adds far more mass than stiffness, making the string more harmonic. Some materials are better than others. Fine silver is used for violins and cellos. Gold is be better. :-)

There was a guy around Princeton who tuned pianos for concertos and quintets that almost changed the character of the music. It would soar. I can't remember more, and the one guy I could have asked is no longer around.

Yeh. :-(

Mine comes and goes.

Jerry

I've agreed so far, but not here. The zero crossings of the comparator's input and output had better coincide in time (with offset allowed for hysteresis). Those squiggles away from the crossings will be suppressed, but they don't matter anyway.

Some wouldn't even call it DSP, but I processed many signals that way for many years.

Jerry

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

I don't think you will see it: the enharmonic amplitude is too small and they run through at different rates. Maybe if you use bass cut to reduce the fundamental it will be visible.

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

Can this feature be retrofitted to s.e.d contributors?

Ahh but Jerry(and others)lurk(s) on comp.dsp ;) The joys of cross posted threads ;}

Cue for Rich to quote the 'Old Lady of Bean'?

That describes it quite well.

The numbers I saw last time I looked at were only an RCH apart at ~19.3 gm/cm^3 (along with tungsten). Osmium, rhenium, iridium and platinum are a fair bit higher; plutonium a bit higher.

Best regards, Spehro Pefhany

This is where multiple methods come in handy. A low-pass filter and zero-cross detection gets you in the ballpark, then your method (looks like a PLL using a phase-accummulator DCO) gets good accuracy.

For a look at the competition (well not quite, you need a PC to run it on), here's a good tuner program with everything:

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Ah! I'm subscribed to comp.dsp. Ain't cross posting fun?

Jerry

I do now. It's a pretty good one for off the cuff, as it were.

Jerry

Not so much flat as dull. Even single notes. Vladimir Horowitz disparaged the notion of changing the sound of a piano by the way one strokes the keys. He said, "There is such a thing as pianistic touch, but it cannot be demonstrated by playing a single note." Nevertheless, if we pretend for now that "touch" matters, a piano corrected for inharmonicity sounds to me as if the pianist were wearing thick felt gloves. The notes have no ... sparkle? We don't have the words. Have you ever improved a stew by adding a little vinegar? Inharmonicity is a piano's vinegar. Hammond organs are harmonic.

Jerry

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

How do they work, then? (The answer 'Very well' is not acceptable.)

snipped-for-privacy@dont-mail-me.com (Robert Scott) wrote in news:426ce85a.8724019 @news.provide.net:

I observed this many years ago using an FFT analyzer. As I recall (25 years ago),I also noticed that the G string on my guitar was actually vibrating at two different frequencies that straddled the desired center. I think this is why I never think that a B created at the 4th fret of the G string ever sounds perfectly in tune with the B string. I attributed this to the fact that the G is a wirewound string and therefore has significant thickness.

As was mentioned earlier, the choice of temperment is always a compromise. The frets contribute to temperment as well, I wonder what the best compromise tuning is for a guitar given all the various parameters.

You might start with the fact that a guitar is usually tuned E A D G B E.

I suppose a smart tuner could have open tuning capabity as well. Open tunings might be easier to consider if you want fifths and thirds etc to be perfect (1.5 vs 1.4983 & 1.25 vs 1.25992)

Piano tuners fight the temperment issue all the time. If I have a piano tuner come out and tune my piano to even temperment (unfortunately, the typical situation), I hate the sound. I used to have a guy who tuned most of the pianos for the recording studios in my area tune my piano. When he did the tuning, my piano sung!

Too bad I can't actually play very well.....

Unfortunately (fortunuately) I have a pretty good sense of pitch.

...

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