DIGITAL GUITAR AUTO-TUNER PROJECT - Page 3

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Re: DIGITAL GUITAR AUTO-TUNER PROJECT
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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
--
Engineering is the art of making what you want from things you can get.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

Re: DIGITAL GUITAR AUTO-TUNER PROJECT

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   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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-----
http://mindspring.com/~benbradley

Re: DIGITAL GUITAR AUTO-TUNER PROJECT
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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.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

Re: DIGITAL GUITAR AUTO-TUNER PROJECT
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Ha!  Another bit of usenet wisdom for my sig file!

--
Jim Thomas            Principal Applications Engineer  Bittware, Inc
snipped-for-privacy@bittware.com  http://www.bittware.com (603) 226-0404 x536
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Re: DIGITAL GUITAR AUTO-TUNER PROJECT
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I wish I had thought of that! (You're welcome.)

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

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

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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
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Re: DIGITAL GUITAR AUTO-TUNER PROJECT

   ...

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Can a piano bridge really twist? One is a long strip glued to the sound
board, the other is part of the cast-iron frame. It astonishes me that
twist has a significant affect.

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

Re: DIGITAL GUITAR AUTO-TUNER PROJECT
PROJECT', on Thu, 28 Apr 2005:

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I don't know if it's significant. The sound board bends in all sorts of
ways, so the bridge might be moved by notes other than the one under
consideration.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
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Re: DIGITAL GUITAR AUTO-TUNER PROJECT

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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
http://www.tki.org.nz/r/science/scienceschool/resources/physical/swingtime_e.htm
Activity 2.

Cheers!
Rich


Re: DIGITAL GUITAR AUTO-TUNER PROJECT
no-one@dont-mail-me.com (Robert Scott) wrote in news:426ce85a.8724019
@news.provide.net:

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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.


--
Al Clark
Danville Signal Processing, Inc.
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Re: DIGITAL GUITAR AUTO-TUNER PROJECT
Try my website:

http://www.pitchanalyzer.com

___________________________________________________________

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Re: DIGITAL GUITAR AUTO-TUNER PROJECT
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A few ads, no substance. How is it enlightening?

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

Re: DIGITAL GUITAR AUTO-TUNER PROJECT
** topposting fixed **
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That must deal with the chemical composition of pitch :-)

--
"If you want to post a followup via groups.google.com, don't use
 the broken "Reply" link at the bottom of the article.  Click on
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Re: DIGITAL GUITAR AUTO-TUNER PROJECT
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Not adequate for musical purposes, I think.  Basically what you're saying is
that the best you can do would result in a 2Hz beat between a tuned string
and the correct pitch; that's still annoyingly out of tune.  Simply tuning
by ear you can get 3 to 4 times better than that (i.e., one beat every 2
seconds).  It might be "close enough for bluegrass," and certainly still
quite an interesting electronics project, but it's not a very good tuner.



Re: DIGITAL GUITAR AUTO-TUNER PROJECT
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I am reading "Musical Acoustics" by Donald Hall, and he has a graph on
page 108 that charts Hz against "JND" (which stands for "Just Noticable
Difference".) Within the frequency range of open strings on a guitar, 1
Hz appears to be 'noticable' for between 60 and 90 dB. For quieter
sounds, it goes up to 3 or 4 Hz. This is for pure sine waves.

Thus, sadly, 2 Hz probably isn't going to be good enough. The maximum
error should probably be 1/2 Hz, as Walter says.

---
Regards,
  Bob Monsen

Re: DIGITAL GUITAR AUTO-TUNER PROJECT
Pet subject of mine as I used to have a pipe organ I built. I could
tell when the tuning was not good but I was not good enough to tune it
by ear. 2 Hz would be horrible, 1/2 Hz poor. The target was to get to
.02 Hz and tune with a strobe display. An array of 16 LEDs is used from
a 16 bit latch which 'freezes' the phase of a clock running 512 times
the desired pitch. The '0' crossing is the clock pulse to the latch
driving the 4-16 decoder. When you're on pitch, the LED pattern doesn't
move, just like a turntable strobe. Generating the scale is tough since
the ratio note-note is 12th root of 2. In '94 I used a 16 bit counter
chain which is OK even when used in the range of 32000 to 64000 but
would likely be better with digital synthesis. The tuner was MIDI in
and out with its own keyboard so I could plug it between the console
and pipework. 'Playing' the tuner turned on the correct pipe to match
the note selection for the strobe. Worked pretty slick.
GG


Re: DIGITAL GUITAR AUTO-TUNER PROJECT
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Yup. But pipe organ is easy (depending on the pipe type), as its
output is quite close to sine wave. Reed pipes are more difficult,
but probably not as bad as the sound from string instruments.

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Nononononnononoooooo! If you tune it to the "even-tempered" scale,
the result is very bad-tempered. All the fifths are bad, all the
thirds are bad.

And here we come to the point where a custom-made tuning tool would
be useful. It is quite easy to go and buy a simple one which just
shows the pitch on a scale. However, I'd like to have one which
can be taught different temperaments.

There are some such instruments available, but they tend to be
rather bulky, eat up a lot of batteries, and cost a lot. On the
other hand, it should not be difficult to use different tempera-
ments once a reliable frequency meter has been made.

---

There are a few challenges which have to be addressed. Here is my
list:

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Re: DIGITAL GUITAR AUTO-TUNER PROJECT

   ...

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Ah, come now! Even in the best of guitars, the frets are located by "the
rule of nineteen". Pianos and fretted instruments have tuning
similarities (although you can't "bend" a piano).

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<aside> Do you know Roland Hutchinson? (He was quite taken with the
selectable temperaments on my recently acquired Yamaha "piano".)

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

Re: DIGITAL GUITAR AUTO-TUNER PROJECT
PROJECT', on Mon, 25 Apr 2005:

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Can this feature be retrofitted to s.e.d contributors?
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
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Re: DIGITAL GUITAR AUTO-TUNER PROJECT
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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
--
Engineering is the art of making what you want from things you can get.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

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