[sdiy] VCO tuning philosophy re-visited

[Richard Wentk]

There's some evidence that stretch tuning sounds more natural generally, because most physical sound generating processes are somewhat inharmonic.

Anecdotally, I used to work in a music shop and we'd occasionally get people coming in and complaining that synths and digital pianos were flat at the top end - even though technically they were perfectly in tune. 

I reliably detune my guitars slightly away from digital perfection, because otherwise there are obvious beats where there shouldn't be beats. So equal temperament is more of a theoretical abstraction than a musical reality.

For analog, you only really need highly accurate linear tuning for FM and other techniques where frequency relationships have a very obvious effect on timbre.

Otherwise, a bit of drift and some non-linearity add character. :)

R

On 7 Feb 2011, at 16:41, Harry Bissell wrote:

> Stretch tuning sound more musical for a piano. whose partials (harmonics) are sharp because of (very significant)
> string stiffness. Playing octaves on a piano sounds 'closer' to being in tune as the beats are more regular, even though the
> actual frequencies are less accurate.
> 
> Of course any sampled synth would sound better with stretch tuning as well (or FM where the harmonics could be 'non-harmonic'
> 
> I don't know about stretch tuning for other sounds...
> 
> H^) harry
> 
> 
> ----- Original Message -----
> From: Richard Wentk <richard at wentk.com>
> To: David <dingebre at 3dphysics.net>
> Cc: synth-diy at dropmix.xs4all.nl
> Sent: Sun, 06 Feb 2011 23:37:03 -0500 (EST)
> Subject: Re: [sdiy] VCO tuning philosophy re-visited
> 
> Stretch tuning sounds more musical than perfect tuning, so you really want the top end slightly sharp and bottom end slightly flat. 
> 
> Although I'm not sure why anyone would want to listen to a VCO running at 16kHz. I doubt anyone over the age of 30 can hear that high. :)
> 
> There are no right answers to these questions because it depends how the synth is used. 
> 
> But generally the mid range is critical - 5 octs from 110Hz up should definitely be reasonably in tune. Outside of the mid-range, absolute accuracy becomes much less critical because you're unlikely to be running the VCO at those extremes, and mistuning at the low end is less obvious than mistuning at the high end.
> 
> Personally I can live with high end mistracking more than I can with an out of tune mid.
> 
> R
> 
> On 7 Feb 2011, at 03:44, David wrote:
> 
>> I know we have hashed this before, but as I’ve now had some time to actually dig into the Steiner VCO (schematics here: http://www.xmission.com/~dingebre/spvco_main_1.4.pdf) and compare it to my Blacet VCO, JH Living VCO, and MOTM Ultra 300 VCO, I’ve noticed a difference in high frequency tracking. Nyle did not have a high frequency adjustment and I’ve noticed that most who do include them typically say they didn’t adjust them (notably JH) or when I’ve tried to adjust them, they tend to mess up mid frequency tracking or have had very little effect. (Ian, I know your VCO tracks over 15 octaves so don’t rub it in  ).
>> 
>> Where can I learn more about high frequency compensation and how it works?
>> Where can I learn more about why high frequencies droop?
>> 
>> Philosophy:
>> Do you tune a VCO for mid range tracking, like over one octave around middle C, and then let the low and high ends fall where they may?
>> Do you tune a VCO for wide range tracking, like over 5 octaves and let the middle range fall where it may?
>> Do you use/adjust/design in to a VCO a high frequency tracking trimmer?
>> If so, does it affect the mid frequency tracking?
>> 
>> Finally, where is the best place to compromise, low end, middle, high, and what percent error is OK musically? To me, even when I measure an exact doubling of frequency from 8kHz to 16kHz, the 16kHz still sounds flat. I’ve tuned the Steiner VCO a dozen different ways, and none sound any better to me.
>> 
>> Have I finally gone over the SDIY insanity cliff… What’s that ringing in my ears?  Stop the noise…. PLEASE STOP THE NOISE………….. ok, that’s better. Now where’s my trimmer adjustment tool, oh there it is, stuck in my ear…
>> 
>> David
>> 
>> David M. Ingebretsen, M.S., M.E
>> Collision Forensics & Engineering, Inc.
>> 2469 E. Ft. Union Blvd., Ste 114
>> Salt Lake City, UT 84121
>> 
>> dingebre at CFandE.com
>> dingebre at 3dphysics.net
>> 801 733 5458
>> 
>> 
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> Harry Bissell & Nora Abdullah 4eva