[sdiy] String synth (solina) and Hammond organ questions

[James Grenert]

Hubert Bollig has done a very nice digital emulation of the B3 using a
Propeller chip:
http://bolltone.de/Projekte/PropB3/PropB3_US.html

He's also done a string synth simulation (but I haven't tried that one yet):
http://bolltone.de/Projekte/PropString/PropStringUS.html

Maybe you could contact him at h.bollig at arcor.de to see if he'd share his
designs.
-J. P.


On Sat, Feb 11, 2017 at 6:51 PM, Michael E Caloroso <
mec.forumreader at gmail.com> wrote:

> Using info pulled from the AH archives, I emulated the Solina chorus
> ensemble effect successfully on my Korg SDD-3300.  Square waves from a
> top octave combo organ system through a highpass filter (resulting in
> a narrow pulse) completes the emulation.
>
> Variations of that string ensemble effect can result in wonderful
> choir ensemble effects.
>
> MC
>
> On 2/11/17, bill bigrig <billbigrig at yahoo.com> wrote:
> > On the Solina, have you seen or heard about Jurgen Haile triple chorus
> PCB?
> > It would give you some reference if you look it up.Rig
> >
> >     On Saturday, February 11, 2017 10:06 AM, "sleepy_dog at gmx.de"
> > <sleepy_dog at gmx.de> wrote:
> >
> >
> >
> >  right, but no I won't forget that, it's on the list (and implementation
> > ideas) :-)
> >  And the percussion mode of course, is also on the list. That definitely
> > adds some of the sound characteristic.
> >
> >  - Steve
> >
> >  Am 11.02.2017 um 17:09 schrieb bill bigrig:
> >
> >   don't forget key click. Rig
> >
> >       On Saturday, February 11, 2017 7:29 AM, Tom Wiltshire
> > <tom at electricdruid.net> wrote:
> >
> >
> >
> >  On 11 Feb 2017, at 14:08, Gordonjcp <gordonjcp at gjcp.net> wrote:
> >
> >  > On Sat, Feb 11, 2017 at 11:42:18AM +0000, Tom Wiltshire wrote:
> >  >>
> >  >> On 11 Feb 2017, at 11:03, Gordonjcp <gordonjcp at gjcp.net> wrote:
> >  >>
> >  >>> What you absolutely must do is ensure that all the notes you
> generate
> > start in phase.
> >  >> <snip>
> >  >>> This is something you'd need to do on a tonewheel emulation, too.
> >  >>
> >  >>
> >  >> Why? The Hammond tone generator is free-running and the pitches are
> fed
> > straight to the busbars. While the frequencies themselves might have a
> fixed
> > phase relationship, it's not related to note onset in any way.
> >  >>
> >  >> Or am I misunderstanding what you meant?
> >  >>
> >  >
> >  > Okay, pull out the 8' bar and play C3.  Holding that down, play C4, on
> > and off a few times.  You'll hear it key on and off, great.
> >  >
> >  > Now pull out the 4' bar as well, and play C4 again.  What's the phase
> > relationship between the fundamental of C4 and the 4' stop of C3?  Can
> you
> > see a situation where you might end up with the two cancelling?
> >  >
> >  > If you were generating all 91 tones, you'd just be gating them on and
> > off.  But in a typical software synth you'd generate each voice
> individually
> > with fixed polyphony.  If you're not careful with it you could easily
> end up
> > with some notes out of phase with others and odd random shifts in tone
> > colour as a result.
> >
> >  Aaah! Yes, ok, absolutely! I see what you mean. Thanks Gordon.
> >
> >  This is a very good point he's making - since the Hammond uses the same
> > tone generator for every/any note, there's no danger of phase
> cancellation.
> > The same is true in the TOG organs/synths. Any "voice based"
> implementation
> > needs to ensure that it copies this effect. This isn't too difficult if
> all
> > the voices are produced on the same DSP, but it makes processor-per-voice
> > implementations a bit awkward to do.
> >
> >  I'd be inclined to run NCOs simulating the correct Hammond pitches for
> the
> > driving/driven gear combinations, and then use shifted versions of the
> phase
> > accumulator to generate the waveform indexes for the required number of
> > octaves. With only a dozen notes, that's not a lot of work.
> >  To adjust the pitches for the standard TOG division frequencies would
> then
> > be a case of tweaking the twelve frequency increments.
> >
> >  Tom
> >
> >
> >
> >
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