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....But only one fundamental at a time, and that fundamentalmad.scientist.jr@gmail.com wrote:
What if it was just for one note (guitar string) at a time?
A guitar string produces many notes.
make it that complicated. I do not think commercial application is the goalsycochkn wrote:
"Eeyore" wrote
mad.scientist.jr@gmail.com wrote:
Thanks to everyone for your replies.
To clarify, the signal would only be from one string.
Would that make it easier to build (such with an analog filter) ?
One string doesn't mean one frequency.
So no.
Band stop filter removes the fundamental, Band pass filter removes the
harmonics. Q and band width determines how much. The filter suggested
does
either. You would need one for each string. You would need to combine the
signals in a simple mixer circuit.
You don't know much about musical instruments do you ?
A single guitar string produces many notes.
Graham
I know what a freaking string does. For playing around you do not need to
A: Which note are you playing?"Todd H" <bmiawmb@toddh.net> wrote in message
mad.scientist.jr@gmail.com writes:
I am looking to build one or more filters that would
1. isolate an electric guitar tone's fundamental tone (ie filter out
the harmonic overtones)
2. isolate an electric guitar's harmonic overtones (ie remove the
fundamental tone)
What kind of filter(s) would I be looking for?
A time-varying non-linear one, best I can tell.
You'll need DSP for this to have reasonable success. The math you're
trying to emulate is quite non-trivial.
Do you have something against analog filters. The filters in the book I
suggested are quite stable inexpensive and not too complicated.
On Thu, 02 Aug 2007 20:18:21 -0000, mad.scientist...@gmail.com wrote:
Thanks to everyone for your replies.
To clarify, the signal would only be from one string.
Would that make it easier to build (such with an analog filter) ?
The problem is that if you want to remove the harmonics well,
you need a very sharp filter. If you had only a single note,
you would tune the filter to put the cutoff just above the
fundamental, so the 2nd harmonic would be well attenuated.
You could select a suitable filter by consulting a filter design
book, which shows the responses of various filter types and
orders (at roughly 2 orders per op-amp stage). What you would
quickly discover is that a really sharp cutoff requires a lot of
stages, and the values of their components have to be really
close tolerance.
But that's for a single, fixed-fundamental note. If you play another
note into that same filter, the alignment won't be correct: If the
new note is a bit lower, its 2nd harmonic will now fall in the
passband of the filter. If the new note is higher, the fundamental
will fall in the stopband.
Don't bother to think about trying to make the filter adjustable
to somehow track the note being played: Such a many-stage
filter with lots of critical components is really tough to adjust
dynamically, but that's not the problem... it's figuring out
what the fundamental is that you want to tune it to! This
is called "pitch tracking" and it is a non-trivial problem.
It's especially difficult for plucked strings like a guitar
because the "2nd harmonic" is not exactly twice the
fundamental, but moves around as the note attacks and
decays. That means that the 2nd harmonic sort of
"rolls through" the fundamental waveform, so simple
schemes that look at waveform zero crossings get really
confused.
Perhaps if you explain what your ultimate goal is, we
can give better suggestions. But basically, you will need
to use digital methods if you are serious about pitch
extraction, and even then this is just "borderline" possible.
Best regards,
Bob Masta
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
This would be for whatever note is currently being played. OneA: Which note are you playing?
It would be nice if this could be variable (ie controlled by a knob)B: How much of its timbre do you want to filter out? How much do you want to keep?
It would be nice to control the amount that is being filtered - so youBTW, did you know that, for most instruments, and the human voice, you can
entirely delete the fundamental, and the sound will still be recognizable?
Build cool gadgets to control tone circuits, light organs and DIYSo, what are you trying to accomplish? Or is this homework? ;-)
On Thu, 02 Aug 2007 18:50:01 +0000, sycochkn wrote:
"Todd H" <bmia...@toddh.net> wrote in message
mad.scientist...@gmail.com writes:
I am looking to build one or more filters that would
1. isolate an electric guitar tone's fundamental tone (ie filter out
the harmonic overtones)
2. isolate an electric guitar's harmonic overtones (ie remove the
fundamental tone)
What kind of filter(s) would I be looking for?
A time-varying non-linear one, best I can tell.
You'll need DSP for this to have reasonable success. The math you're
trying to emulate is quite non-trivial.
Do you have something against analog filters. The filters in the book I
suggested are quite stable inexpensive and not too complicated.
A: Which note are you playing?
B: How much of its timbre do you want to filter out? How much do you
want to keep?
BTW, did you know that, for most instruments, and the human voice, you can
entirely delete the fundamental, and the sound will still be recognizable?
So, what are you trying to accomplish? Or is this homework? ;-)
Good Luck!
Rich
get one of those korg "guitars" with the nylon strings and MIDI output.I am looking to build one or more filters that would
1. isolate an electric guitar tone's fundamental tone (ie filter out
the harmonic overtones)
2. isolate an electric guitar's harmonic overtones (ie remove the
fundamental tone)
What kind of filter(s) would I be looking for?
I'm afraid that pitch tracking of a guitar will never be cheap orThanks for the explanation - that makes sense.
I have a couple of applications/projects I'd like to do.
Application #1 would be pitch tracking. This could be for controlling
a tone generator circuit - ie play a low 'E' on the guitar, and you
hear a low 'E' from the tone generator. I know there are MIDI pickups
and interfaces for this, but I'm interested in working on something
from scratch and keeping it cheap/simple if at all possible. If I want
to simply control a synth with a guitar I can buy a MIDI interface &
keyboard.
You don't need pitch tracking for this... plain old static filtersAlso, another thing I might use pitch tracking for is to
control a color organ type device - different notes would light up
different LEDs.
Again, you'd need the output of the pitch tracker to control theApplication #2 would be an effects pedal that removes the fundamental
tone of whatever note is currently being played, or in a different
setting, ONLY plays the fundamental tone of whatever note is currently
being played.
Hmm. Well in that case, what would stop you from setting up such aAlso, another thing I might use pitch tracking for is to
control a color organ type device - different notes would light up
different LEDs.
You don't need pitch tracking for this... plain old static filters
will do fine, a sharp (and stable) bandpass for each note.
On Fri, 03 Aug 2007 21:54:37 -0000, mad.scientist...@gmail.com wrote:
Thanks for the explanation - that makes sense.
I have a couple of applications/projects I'd like to do.
Application #1 would be pitch tracking. This could be for controlling
a tone generator circuit - ie play a low 'E' on the guitar, and you
hear a low 'E' from the tone generator. I know there are MIDI pickups
and interfaces for this, but I'm interested in working on something
from scratch and keeping it cheap/simple if at all possible. If I want
to simply control a synth with a guitar I can buy a MIDI interface &
keyboard.
I'm afraid that pitch tracking of a guitar will never be cheap or
simple with analog methods. Over the years I've seen a lot of
schemes attempted (and tried a few of my own), and none of them
exactly set the world on fire. Normally, you would need to have
a good pitch tracker to control the filter cutoff to remove harmonics,
not the other way around. I recommend you try a simple
zero-crossing or threshold-type detector to get a feel for this
"non-2nd harmonic" problem. Feed the signal into a comparator
and listen to the "square" wave output (and watch it on a scope).
If everything worked as hoped, the output would have only one
zero-crossing per cycle and would be relatively easy to convert to
a DC level representing pitch. But alas, this only seems to be
true for certain portions of the note, breaking at others into a
buzz as the second harmonic confuses the detector. Since
it isn't truly twice the fundamental, you can't find a threshold
that will produce only one zero-crossing per cycle.
Also, another thing I might use pitch tracking for is to
control a color organ type device - different notes would light up
different LEDs.
You don't need pitch tracking for this... plain old static filters
will do fine, a sharp (and stable) bandpass for each note.
Application #2 would be an effects pedal that removes the fundamental
tone of whatever note is currently being played, or in a different
setting, ONLY plays the fundamental tone of whatever note is currently
being played.
Again, you'd need the output of the pitch tracker to control the
filter cutoff. Catch 22!
Believe me, many, many folks have spent many, many hours on
this problem.
Best regards,
Bob Masta
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
42 fixed filtersI am looking to build one or more filters that would
1. isolate an electric guitar tone's fundamental tone (ie filter out
the harmonic overtones)
2. isolate an electric guitar's harmonic overtones (ie remove the
fundamental tone)
What kind of filter(s) would I be looking for?
Does anyone know if schematics for these devices (the simpler the
better) are available online?
Thanks...
Nothing but the cost. You'll probably have to tune each filter to allow forHmm. Well in that case, what would stop you from setting up such a
bandpass filter for each note and using it to trigger a tone generator
instead of an LED?
This is one of those things that sounds good at first, but when youThanks for the explanation - I think I understand.
Also, another thing I might use pitch tracking for is to
control a color organ type device - different notes would light up
different LEDs.
You don't need pitch tracking for this... plain old static filters
will do fine, a sharp (and stable) bandpass for each note.
Hmm. Well in that case, what would stop you from setting up such a
bandpass filter for each note and using it to trigger a tone generator
instead of an LED? This would serve the purpose of simple pitch
tracking, no? It would only be capable of tracking notes in half step
intervals (no string bends or anything) but that would probably serve
my purpose. Would that work?
On Wed, 08 Aug 2007 18:47:59 -0000, mad.scientist...@gmail.com wrote:
Thanks for the explanation - I think I understand.
Also, another thing I might use pitch tracking for is to
control a color organ type device - different notes would light up
different LEDs.
You don't need pitch tracking for this... plain old static filters
will do fine, a sharp (and stable) bandpass for each note.
Hmm. Well in that case, what would stop you from setting up such a
bandpass filter for each note and using it to trigger a tone generator
instead of an LED? This would serve the purpose of simple pitch
tracking, no? It would only be capable of tracking notes in half step
intervals (no string bends or anything) but that would probably serve
my purpose. Would that work?
This is one of those things that sounds good at first, but when you
get down to details there are some problems (besides the cost, as
another post mentions). The main problem is that you will need
very sharp tuning to isolate each note. If you build a simple
bandpass for each note, the "passband" must be very narrow
in order to reject adjacent notes... but then it will reject the
desired note if it is not dead-on. So you need a multi-pole
bandpass that has a flatter top and still has steep slopes.
These get complex and fussy to tune.
But suppose that is not a problem. (Actually, there are
digitally tuned single-chip filters that could handle this,
where the fitler frequency is controlled by a clock. This
could be made very accurate using a crystal reference.)
Then you will discover the hidden "gotcha": The response
time of a filter is proportional to the inverse of its bandwidth,
which means there will be a lag between the time you pluck
the string and the time the peak comes out of the bandpass.
Then, if that wasn't bad enough, remember than the bandpass
output is still AC, and for a guitar most of the notes of interest
are in the 100 Hz or less range. If you are going to convert this
to a DC value you will need further smoothing after you (full-wave)
rectify it, further adding to the delay.
OK, maybe with one filter per note you don't really need to convert
to DC, just some sort of a threshold comparator. But you will have
to have some way to keep the subsequent synth oscillator going
between comparator peaks, which means a time delay on the
shut-off... probably much better than delaying the onset.
Anyway, as a rule of thumb, figure that an overall 10 msec onset
delay will probably be the upper limit of tolerability. You might be
able to tolerate more if you use the synth as a backup instrument
that echoes your leads with a slight reverb-like lag. A 10 msec
lag is roughly what you'd get from a 100 Hz passband, but the
actual passbands you need are much narrower because each
semitone is only 6% from its neighbors. So at 110 Hz you need
passbands that are only 17 Hz wide, which means a lag of
roughly 59 msec... pretty bad. And it gets worse for lower notes.
Still, despite all this gloom and doom, I strongly encourage you
to play around with this idea. Start with a simple single-note
bandpass and see what you can do. You might come up with
some clever workaround for the above problems that other
folks haven't thought of yet, or you might not... but you'll have
a fun and educational experience that will almost certainly lead
to other insights and maybe to other inventions.
Best regards,
Bob Masta
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
---Todd H wrote:
"sycochkn" <sycochkn@earthlink.net> writes:
"Todd H" <bmiawmb@toddh.net> wrote
mad.scientist.jr@gmail.com writes:
I am looking to build one or more filters that would
1. isolate an electric guitar tone's fundamental tone (ie filter out
the harmonic overtones)
2. isolate an electric guitar's harmonic overtones (ie remove the
fundamental tone)
What kind of filter(s) would I be looking for?
A time-varying non-linear one, best I can tell.
You'll need DSP for this to have reasonable success. The math you're
trying to emulate is quite non-trivial.
Do you have something against analog filters. The filters in the book I
suggested are quite stable inexpensive and not too complicated.
I love analog filters when they're appropriate solutions to the
requirements.
Now, if you have an analog filter that'll satisfy these requirements,
write it up in dissertation form, take a few classes, and a Ph.D. in
Electrical Engineering is well within your grasp. Otherwise, I'll
simply suggest that the requirements as stated are somewhere between
"ill suited to analog" and "provably impossible in analog."
Pretty damn hairy even in DSP.