[sdiy] "Living VCOs" PCB in 2009 ?

[nicolas]

Tuning is a very deep topic which I won't even pretend to be expert in, but I would point out that while synths are generally tuned according to a strict chromatic scale where every octave is exactly a doubling in frequency, many other instruments are not.

In particular pianos and good human singers tend to very slightly stretch the octaves, so that at the top end they are very slightly sharper than you might expect and at the bottom end very slightly flatter.  Also the amount of detuning in pianos between the two or three strings that make up each note is carefully adjusted to maximise the sustain time.  There is a magical tiny amount of detuning that sustains longer than perfect unison.

These tuning oddities in the piano world probably educate our collective ear to expect it.  And so a synth sounds more plausibly musical when it also deviates by a similar amount.  Maybe that is why we love some synths more than others - because they can more easily achieve just the right amount of tuning deviation.

Cheers,
Nicolas


--- On Wed, 10/12/08, Dave Manley <dlmanley at sonic.net> wrote:

> From: Dave Manley <dlmanley at sonic.net>
> Subject: Re: [sdiy] "Living VCOs" PCB in 2009 ?
> To: "JH." <jhaible at debitel.net>
> Cc: synth-diy at dropmix.xs4all.nl
> Received: Wednesday, 10 December, 2008, 11:19 PM
> JH. wrote:
> >> Now if somebody is designing a new unstable VCO,
> >>     
> > Just to clarify: I have nowhere described my JH-5 VCOs
> as "unstable".
> > In fact, if you read the short text at the link
> I've posted, I'm talking about quite the opposite.
> > 
> > JH. (puzzled)
> >   
> The problem with this discussion is the use of the
> subjective term "living".  The term conveys no
> technical information, and has caused the discussion to
> "go off in the weeds" in a number of different
> ways.  I don't know if you are intentionally or
> inadvertently not providing this key definition in a more
> straightforward manner.   The term obviously has some
> specific meaning to you, which is unknown to the list,
> mainly because I don't think list members read the text
> you referenced in your original post.  From your JH5 page we
> read:
> 
> "My goal was to build a set of VCOs that have the
> untamed bass range power of early EMS and Moog VCOs, but
> which are tracking a keyboard voltage over 5 or more octaves
> nevertheless. I found that "untamed" Beating in
> the bass range /and/ controlled beating in higher octaves is
> not possible with standard exponential 1V/Oct oscillators. A
> good part of that special sound of early Moog and EMS
> oscillators is not because of any "randomness",
> "unstability", "instability" or
> "noisyness", as so often is said. A good deal of
> their behavior /is/ because of that, but it is not the whole
> story. There are also some very deterministic factors in
> these old circuits which have been unpleasant side effects
> for the designers back then, but which are worth a closer
> analysis when we're designing a musical VCO today. This
> is implemented in form of three "linear detune"
> potentiometers on the JH-5A VCOs."
> 
> See: http://jhaible.heim.at/jh5/jh5.html
> 
> From this one *might* conclude that linear, as opposed to
> expo, detuning is the key to the 'living VCO'.
> 
> I recalled an old submission you made regarding a linear
> detuning modification to the Oberheim SEM.  Digging in my
> files I found a copy from July 10, 1997 which is archived
> here:
> http://web.archive.org/web/20051220015016/http://home.swbell.net/roy_tate/info/lindetun.html
> 
> The key thought at the end of that post: "...I just
> wanted to show that there might be some *tendency*, some
> *trend* from very rich sounding synths at one end to very
> precice sounding instruments on the other end. And that the
> reason for this is not black magic, but of some physical
> nature. And, that this may have something to do with a
> linear term in VCO detuning."
> 
> Many expo VCO implementations include a linear modulation
> CV port, and so on to the next question: does the
> 'living' VCO do more than provide a knob to adjust
> the linear detune amount?
> 
> -Dave
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