[sdiy] Interesting article on top octave generators.

[Mike Bryant]

I've always shipped my custom 'all digital since 1984' synths with Railsback as one of the tuning options.  I know that it has definitely been used on several film scores.

________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of rburnett at richieburnett.co.uk <rburnett at richieburnett.co.uk>
Sent: 04 January 2025 20:22
To: Ben Stuyts <ben at stuyts.nl>
Cc: Synth DIY <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Interesting article on top octave generators.

Perhaps so that it doesn't sound out of tune at the top end when played
alongside a real piano that's been tuned according to the Railsback
curve.

-Richie,


On 2025-01-04 19:16, Ben Stuyts via Synth-diy wrote:
> Thanks for the insight, Don, I did not know that was the reason for
> it.
>
> But why would stretch-tuning (as Roman says) be an option on synths
> like the P6? The harmonics there would always be integer multiples
> from the fundamental and there would not be any inharmonicity. That
> would only make sense if it sounds somehow ‘good’ to our ears.
> Which is more or less what the Rhodes manual says. Or is this purely
> to compensate for some flattening at the high end because of flaws in
> the VCO circuitry?
>
> Ben
>
>> On 4 Jan 2025, at 19:05, Donald Tillman <don at till.com> wrote:
>>
>> That quote from the manual is misleading.
>>
>> In string instruments the harmonics of the note run slightly sharp.
>> This is because the endpoints are a little less flexible than the
>> rest of the string.  Just plug an electric guitar into an
>> oscilloscope and it's pretty easy to see the harmonic frequencies
>> scooting to the left of the fundamental.
>>
>> So pianos are stretch tuned so that, if you're playing octaves, the
>> harmonics of the lower notes are in tune with the fundamentals of
>> the higher notes.  The amount of stretch depends on the string
>> length, tension, and physical characteristics, so each instrument
>> model is different, and so traditionally they come with a chart like
>> that.
>>
>> And the effect is similar for electric pianos with tines (Rhodes) or
>> reeds (Wurlitzer).  But not for organs.
>>
>> So stretch tuning in the synth world would only make sense if you
>> could generate slightly sharp harmonics.  Other than physical
>> modeling, say a Karplus-Strong model tweaked for less flexibility at
>> the endpoints, I don't see how that would work.
>>
>> https://en.wikipedia.org/wiki/Stretched_tuning
>>
>> -- Don
>>
>> --
>> Donald Tillman, Palo Alto, California
>> https://till.com
>>
>>> On Jan 4, 2025, at 9:09 AM, Ben Stuyts via Synth-diy
>>> <synth-diy at synth-diy.org> wrote:
>>>
>>> All this discussion about tuning and temperaments reminded me of
>>> the Fender Rhodes service manual, where they take a dive into
>>> stretch-tuning. See
>>> https://www.fenderrhodes.com/org/manual/ch5.html#5-3
>>>
>>> Quote: "Stretch tuning is a procedure widely followed by the piano
>>> tuning profession. It recognizes a phenomenon of the human ear
>>> whereby tones in the upper range of a keyboard will sound "flat"
>>> even though they are calibrated with extreme precision.
>>> Fortunately for all, a consensus has long since been agreed upon
>>> as to the exact amount of stretching. A piano so tuned creates the
>>> impression of great tonal brilliance."
>>>
>>> With this chart:
>>>
>>> <Stretch Tuning Chart.jpeg>
>>>
>>> This obviously can never be done with the divide by 2 approach.
>>>
>>> But are there any analog VCO’s (or synths) that actually
>>> implement some sort of stretch tuning? (Aside from the unwanted
>>> flattening in the high end which is opposite from stretch tuning.)
>>>
>>> Ben
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