[sdiy] guitar pitch detection, was: Mighty quiet lately...

[Paul Perry]

No pitch conversion strategy can be a "waste of bandwidth"
on SDIY - because, wherever there is an input and an output,
there is an opportunity for music (of some kind!) to occur.
I am sure that some of the best circuits have evolved from
attempts to build something quite different, like the classic 
fuzz circuit that bears a suspicious resemblance to an early 
applications note preamp. I guess that SDIY like music in 
general depends on us bing alive to the possibilities.

Though I suspect that attempts to build the ideal pitch to
voltage converter, like attempts to build an infinite sustain 
guitar or to trisect an angle with a compass and rule, have 
destroyed better minds than mine.

paul perry Melbourne Australia


----- Original Message ----- 
From: "John Richetta" To: "Synth DIY" <synth-diy at dropmix.xs4all.nl>
Sent: Monday, October 04, 2010 12:11 PM
Subject: Re: [sdiy] guitar pitch detection, was: Mighty quiet lately...


> On Oct 3, 2010, at 5:32 PM, Paul Perry wrote:
>> The problem is not detecting the pitch - it is detecting the pitch  
>> QUICKLY, and by quickly I mean within less than a full cycle.
> 
> Ah, fair enough summary, and I guess did already knew that, having  
> played with some gear that does this.  But even the better gear I've  
> played seems to still be somewhat glitchy - VG88, VF-1, GR-1, etc.   
> So, perhaps there is still some room for improving pitch detection  
> reliability?
> 
> An unstated assumption in what I wrote was that I wasn't expecting  
> miraculously fast pitch detection - I presume any DIY analog circuit  
> will be far from ideally fast, and will probably need to be used in  
> combination with relatively direct signal, or else played in a studio  
> type situation (where delay can perhaps be better tolerated and  
> compensated for).
> 
>> Can it be done?
>> Yes - if you track the exact position of each string, and use
>> this information to drive a DSP modelling algorithm. I believe this  
>> approach has been used successfully.
> 
> Sure; now that you mention it, I do recall hearing that about the  
> VG-88 (and kin).
> 
> Note that, strictly speaking, detecting wave slope even for less than  
> a full cycle (as is necessary primarily for low notes) is not  
> *necessarily* different than measuring the output response of some  
> filter.  That is, a tuned filter responding to this input might  
> correctly identify it as being in the right range pretty quickly  
> (though I must admit that the control would need to be smarter than I  
> describe to do that).  Obviously, practical comb filters do incur  
> especially egregious delay, and generally speaking, using the  
> knowledge of how waves propagate down a string, especially initially,  
> is useful for fast response.
> 
> So, yeah, what I described is probably junk - it certainly doesn't use  
> that info.  Sorry for wasting the bandwidth.
> 
> -jar