[LAD] GuitarSynth

Tim E. Real termtech at rogers.com
Mon Apr 27 23:57:38 UTC 2015

On April 27, 2015 07:59:36 PM Ralf Mardorf wrote:
> On Fri, 24 Apr 2015 23:13:12 -0400, Tim E. Real wrote:
> >To reduce latency I even tried putting the guitar through a standard
> >time-domain pitch shifter (up one octave) and then into the detector.
> >Not bad, so so.

> Since "dead" strings aren't an option for me, this is something I'll
> test for monophonic converters, because they also suffer from
> accuracy and latency. I never tested this. Nice idea.

The purpose there was to shift the guitar up one octave before
 it goes into the polyphonic detector, so that I could reduce
 the number of FFT bins required and therefore reduce latency.

It worked better, kind of OK, but if you know standard 
 time-domain SOLA pitch shifters, they leave artifacts in the sound,
 so it's not an ideal solution.
A nice frequency-domain pitch shifter would be better - very little
 artifacts in the sound - but these shifters have large latency,
 so that cancels the purpose of this because time-domain 
 SOLA shifters have very little latency, but just the artifacts.

> JFTR, if I'm short of money, I boil "dead" guitar strings in water. As
> long as they only suffered from skin fat and particles of skin and they
> aren't worn out or suffer from oxidation, this refreshes the strings
> without a side effect.

Aw jeez, sad situation, buy a new set of strings, eh :-(
If you lived in my city I'd give you a pack!

Yeah I tried boiling them a few times long ago.
All that really seemed to do was bring out the rust even more!

I've always believed it's not so much the dirt or oxidation on the 
 string which is the problem:
That simply makes it appear like a slightly thicker string and thus
 the tuning changes slightly. Most of the dirt can be removed.
The real problem is the dozens of small 'cuts' along the string length
 that are accumulated over time from bending, or just playing, against
 metal frets. This produces horrible overtones. The single fundamental 
 frequency of a given fret position begins to 'split' into two or more 
 fundamental frequencies. Ugly.

Just a side 'note': A tip for players out there:
There is a tendency to think that one should adjust the pickup as close 
 as possible to the strings without touching them, for maximum output.
Seems reasonable right?
But no, don't do that. Because the strings then sit in a less linear
 portion of the magnetic field - on the 'down swing' they are attracted 
 much more to the pickup magnet than on the 'up swing'.
The result is mechanical nonlinear string motion, resulting in...
 split fundamental frequencies.
The effect is striking. You can hear it without even plugging the guitar in.
As you adjust the pickup ever higher, and pluck the strings, you can
 hear the horrible overtones from the frequency splitting. 
It's really gross sounding. So be careful.
Enjoy your day :-)


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