reliable pitch tracking

[orgaqualia]

How is it done?
I'm kind of new to this hobby but I have built a couple of projects (lavarim2, blue magic, controll fuzz). I really want to build something that can track pitch.
Is it doable?
Where can I get info on it?
By the way... I love this board. I have learned lots here. Thanks!
-db-

[Dave_B]

Basically, pitch tracking can be accomplished with a circuit that can measure the frequency of a string, then do something usable with that measurement.  Guitar tuners and Guitar synths are common example.  It's not a simple thing to diy, though. 

This will get out of my depths pretty quickly, but what do you want to do with the pitch tracking? 

[Somicide]

Isn't most pitch tracking done digitally?  I'd think it'd be easier, IMO.  Methinks the OP is looking for some kind of harmonization device.

[calpolyengineer]

Well you might be interested in this little ditty courtesy of Mr. Mark Hammer. http://hammer.ampage.org/files/GuitarP2V.PDF

This is an old Penfold circuit that turns a pitch into a control voltage. It is intended to be a guitar to synth interface but there is no reason you couldn't use the control voltage to do other things.

-Joe

Also, if you are interested in making a harmonizer, here is one that was posted on Mark Hammer's site too.
http://hammer.ampage.org/files/EMMHarmoGen.PDF

[Somicide]

To clarify:  I didn't mean it'd be easier to DIY a digital pitch tracker, merely it would take less physical pieces 'n such.

[StephenGiles]

http://img.photobucket.com/albums/v317/StephenGiles/EHsynth1.gif

To do it the analogue way, you must have a decent sine wave extracted from the guitar signal, whch you can get using this circuit - not small! Then you need pitch to voltage conversion and tracking VCOs - wanna give up???

[Joe]

http://www.diystompboxes.com/analogalchemy/pedals/shocktave.html

The 3rd stage is a frequency-to-voltage converter, the voltage appearing at the base. A resistor + cap in parallel may be placed from base to ground, with a transistor buffer also direct-coupled to the base. This prevents loading of the output. (The Shocktave skips the buffer, but...) The input signal needs preamplification so the diode conducts with each signal peak.

Let's say you wanted to make a crude tuner. The RC network is designed to have a peak frequency response at 440Hz. The transistor buffer is used to drive an LED which becomes the brightest when the A string is in tune.

[orgaqualia]

Thanks for the info...
I want to do stuff like:
yes, maybe some harmonization,
a filter that tracks the pitch of the signal, sort of a state variable eq depending on freq,
a more musical freq mod, where the modulation frequency is derived from pitch info,
distortion that is (yet again) freq dependant...etc

I have been thinking about this for a while and I was just wondering what could be done that isn't some variation on clipping, filtering or delaying the composite signal.I am aware of the quadra fuzz and the guitar p2V article. I had thought about using resonant networks for this and it seems like it would work in principal, but for real accuracy the signal would have to be in "tune" with the circut, not to mention that I would need a network for each note.

Do you all think that I should play around with this? I realy have very little experience with electronics in general, but I do understand the more abstract side of things. I'm hoping that your real world experiences can shed some light on the practical feasability of this(resonant network) sort of thing.
-db

[orgaqualia]

By the way, that EH thingy looks pretty interesting. How well does it perform?

[Mark Hammer]

Generally speaking, the narrower the bandwidth of the signal that the pitch tracker has to interpret as possibly being the note, the easier it is to detect the note pitch.

I recently bought an old Roland GK-1 pickup and MIDI brain.  I was not prepared for the time difference in pitch tracking on the low vs high notes.  Keep in mind that several peaks are usually needed to assure accurate tracking.  Of course compare how many milliseconds it takes for measuring the interpeak interval for a low E vs a 12th fret high E on the unwound E string.