Polyphonic Minimoog Model D

[CZ Rider]

So what if you could somehow split the three Model D oscillators to play polyphonicly from a keyboard?
I have tried the three or more Minimoog model D's or the polychained Voyagers. None of these solutions seemed like that great of a polyphonic instrument. For the Model D's one would have to change the panels on every voice to adjust the patch. Not the easiest or practical way to get a polyphonic Moog. And three oscilators times X amount of voices gets muddy quick. So how about just using one Model D and splitting up the oscillators? Same voice, just a different way to access the tuning of each oscillator.

First one would have to get seperate CV inputs to each of the three oscillators. For the standard second version of the oscillator board this is easy to do. (The middle CA3046 version.) Back in the day this mod was neded for patching in a Sequential Circuits Model 700 programer.
Here is the SCI drawing of the mod:


Next needed is a way to patch it up. The MOTM-650 MIDI to CV is a four voice module that is perfect for the job. It had one interesting poly mode called UNISON STEAL where one note plays all four outputs. Two notes splits the four outs so the first note is 1 and 2 while the second is 3 and 4. And three notes down splits 1, 2, 3, and four notes 1, 2, 3, 4.
Luck for me I have an MOTM-650 in my Minimoog/modular cabinet and individual CV ins for each Mini oscillator. The patch involves adding together all the S-trigger outs for the four channels. And patching in Channel 1, 2, 3 to oscillator 1, 2, 3 CV inputs.
The patch looks like this:


So what does it sound like? How does it play?
Surprisingly well and it sounds bad ass! The algorithm used in the MOTM-650 is very playable. It has note memory so unlike the analog way of splitting two ocillators with high/low note priority, the chords stay when released. Takes a bit of practice like anything, but the response is very predictable and therefore very playable.
Here is an MP3 sample of the polyphonic three note, single voice Minimoog Model D:
Polyphonic Model D MP3 file 3 minute demo
I have been playing a Minimoog since 1974. Just when I thought I have heard just about every sound it can make, this opens up a whole new instrument. This method keeps the original Minimoog voice, just allows a different way to access the tuning of the oscillators via a keyboard.

[JohnLRice]

WOW! Great mod, CZ! Sounds wonderful!! :hail:

Great "ploy" to make the Mini D polyphonic! (was that a typo on Picosong or intentional? "CZ Rider - Ployphonic Minimoog Model D"

[noddyspuncture]

Great stuff Terry...!

Cheers,
Tom

[CZ Rider]

was that a typo on Picosong or intentional?

Ooops! Typo, fixed it! Was up late playing my new ployphonic Minimoog and realized I had to get up for work in a few hours and typed quickly.
The MOTM-650 unison steal works great for that and would also work on an ARP 2600 or similar modular. Hope the audio file demonstrates how the single monophonic lines have all three oscillators in unison, so the Minimoog has the same balls. And only splits up the oscillators when 2 or 3 keys are held down. Have to play clean though and not hit any of the cracks. Triggering could be tricky if not using S-triggers as they are easily added together as "AND" gates. Might need another way to add positive gates. One of the advantages of the S-trigger system.
That Minimoog is a new instrument though. Going to be tough to go back to standard triggering. Too bad they did not think to implement such a mode on the mostly digital controlled Voyager. Much easier to do with a digitally scanned keyboard controller. Still can't believe just how different the Poly-Mini sounds with the same VCO/VCF/VCA setup.

PS: Still reads Ployphonic on the MP3 ID tag though?

[lancearm71]

Holy smokes you guys went to a lot of work to get a polyphonic Mini!
I started that quest in the 70's. I managed to turn one of my mini's into a 3 note polyphonic synth. It would sound all 3 osc's when you played one note, but started splitting them off when you'd play 2 or 3 notes.
I bought a 4 octave Pratt-Reed keyboard and modified one of my minimoogs oscillator boards so each osc also accepted external voltages, not just the one coming in at the top jack. I built a keyboard scanning circuit in 74, probably before anybody else did, and with just discrete digital IC's from TI, a DAC resistor ladder, sample and holds, and some voltage tuning opamps, whalla I had a 3 note polyphonic Minimoog. I actually did call and talk to Bob Moog about it. By the way, he personally sold me that particular minimoog in 72. What a neat guy. We were both engineers so we had a lot to talk about.
Well, I wound up restoring that MiniMoog back into it's original form. But I did leave the visual tuning leds and circuits in. By the way I did build an auto tune circuit, but I hated it. It phase locked the osc's, and as you can image it sounded too thin. Even when I controlled the offset, it sounded too regular. The fact that the oscillators don't track perfectly leads to it's more natural and great sound across the keyboard. No I never bought the upgraded osc boards. I just kept my mini's in tip top shape with regular maintenance. I did replace the tuning pots with military grade 20turn pots. (after all I was a DOD design engr..brag brag)
I need to post pictures of my minimoog front panels. They still have the tuning LED's on them, and yes they work. I needed them for all the ELP music I use to play. In playing Hoedown with one mini, you have to start with the 1st and 2nd tuned a fifth apart, and the 3osc like a drone note. THen after the intro you had to flip switches and tune the osc's to the about the same pitch, all while playing the fast Hammond organ parts. With the LED's you could tune visually. I'd also use that technic for 3rd Empression at the end, and for Aqua Tarkus.
I got kind of off subject here, but this all kind of relates to a polyphonic Mini.
I also have the intended student configuration of the sonic 6 moog. As some of you know it played 2 notes. I brought the 2 osc control voltages out, using 1/4" jacks, and ran those to 2 minimoogs. Talk about a massive Moog sound back before polyphonic was the norm. I still have all that. By the way, the sonic osc's all track one key played, but split when you play 2 notes. It's a pretty cool sound. I actually have a song online (Life Beyond LA, Ambrosia) using that 2 note sonic sound. Only one osc follows the glide setting, and it's exponential, all that sounds pretty cool.

[jsharpphoto]

Not to split hairs, because this is certainly awesome, but wouldn't this be paraphonic, not polyphonic? Since all three voices share the same filter and envelope? Or is it technically "poly" because each oscillator has its own wave form?

[lancearm71]

Actually that's right jsharpphoto. The 3 osc's still fed to the mini's mixer/filter & envelope generators. These days I'll use a Mini VST if I want a poly mini sound. But when playing live, there's nothing cooler looking than tweaking the panel of a Moog on stage.
I attached a picture of the tuning LED's I still have on my minimoogs. There's also a pair above the Tune knob which syncs to the 440osc.

Minimoog with tuning LEDs

[jsharpphoto]

Actually that's right jsharpphoto. The 3 osc's still fed to the mini's mixer/filter & envelope generators. These days I'll use a Mini VST if I want a poly mini sound. But when playing live, there's nothing cooler looking than tweaking the panel of a Moog on stage.
I attached a picture of the tuning LED's I still have on my minimoogs. There's also a pair above the Tune knob which syncs to the 440osc.

IMG_7062.JPG

to be honest, I think I actually prefer the sound of paraphonic to polyphonic. and it's certainly easier to manipulate.

[noddyspuncture]

I needed them for all the ELP music I use to play. In playing Hoedown with one mini, you have to start with the 1st and 2nd tuned a fifth apart, and the 3osc like a drone note. THen after the intro you had to flip switches and tune the osc's to the about the same pitch, all while playing the fast Hammond organ parts. With the LED's you could tune visually. I'd also use that technic for 3rd Empression at the end, and for Aqua Tarkus.

Can you point us to any videos and/or sound recordings of you playing those ELP numbers you mention please?
I also play in an ELP tribute so am particularly interested....

Cheers,
Tom

[sbell.sd]

Had my minimoog modified ~1980, adding individual inputs to each oscillator. A couple of years ago I made a midi to cv box. It adds much more than I had expected.
With only one note depressed on the MIDI keyboard oscillators 1, 2 and 3 play that note
With two notes depressed oscillator 3 continues to play the first depressed note and oscillators 1 and 2 play the second note.
With three notes depressed oscillator 3 continues to play the first depressed note, oscillator 2 continues to play the second note depressed and oscillator 3 plays the last note depressed. When notes are released they hold their current notes.
With any note depressed the midi to cv box sends a S-trigger to the minimoog.

Chords sound good (even) with equal-temperament (which due to its nature of being somewhat mistuned) brings the rolling of the oscillators.
Opens a new depth, and can still be played monophonically (playing only 1 at a time) although with the oscillators well tuned it sounds some what thin comparatively.
Really wouldn't go back.

Think Moog missed the bus on this--should have at least made a feature like this available in the new voyagers and minis that have digital keyboards.

[stiiiiiiive]

I’d love to see a video of that