[sdiy] questions on string synthesizers

[Elain Klopke]

>I think they are essentially the same as old organs - the basic approach
is to generate a square wave for each note, then optionally use a fixed
filter (often just a resistor and a capacitor/inductor) to produce various
different tones, then optionally combine those tones for each key to
produce different timbres.

Is there anywhere that shows what filter frequencies to use for what
instrument?

On Sun, Feb 19, 2017 at 7:08 PM, Adrian Corston <eidorian at aladan.net> wrote:

> I think they are essentially the same as old organs - the basic approach
> is to generate a square wave for each note, then optionally use a fixed
> filter (often just a resistor and a capacitor/inductor) to produce various
> different tones, then optionally combine those tones for each key to
> produce different timbres.  The details of how this is done (which is what
> you're actually asking about) varies from machine to machine - older
> designs used multiple poles on the key switches to allow the tones to be
> combined; newer designs used note keying chips which did the combining
> internally.  There are almost certainly other techniques I don't know about.
>
> Many stringers also had effects such as phaser circuits, BBD-based chorus,
> and vibrato (achieved by varying the clock on the top octave generators) to
> produce the classic "string machine" sound.
>
> Fun fact: some organs produced white noise for their drum machines by
> combining many unrelated (dissonant) tones (somewhat like the TR606/DR-110
> cymbal sound that was generated by combining 6 square wave oscillators).
>
> The one thing I haven't been able to fully understand is how they did
> fully polyphonic A/R envelopes.  I've been meaning to have a look at some
> schematics at some stage but haven't gotten around to it yet.
>
> Cheers,
> A.
>
>
> ----- Original Message -----
> From:
> "Elain Klopke" <functionofform at gmail.com>
>
> To:
> <synth-diy at synth-diy.org>
> Cc:
>
> Sent:
> Sun, 19 Feb 2017 15:31:17 -0600
> Subject:
> [sdiy] questions on string synthesizers
>
>
> How do the selectors for the various sounds work? Like with the violin and
> cello, trumpet and tuba tabs or stops, you press the button and you hear an
> aproximation of a violin sound, and you can add in the rest of the sounds
> to get something orchestral. How is the string synth taking the raw output
> from the top octive chip and subsequent dividers and transforming it into
> the various instrument sounds? I assume there's some sort of filtering
> going on, but I can't quite wrap my head around it.
>
> thanks,
>
> -Ian
>
>
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