Building blocks for organ simulation

[pdavis68]

In the spirit of the EHX B9 and C9 pedals, I'm interested in messing around with this sort of idea. I don't know if theirs is digital or not. I'd be more interested in an analog approach, however.

Can anyone give me an idea of what the building blocks might be for something like this?

I'm assuming to begin with I'd need a VCF, LFO and envelope filter. Would that be enough to get me on the road to it? Am I missing any key components?

It doesn't have to be any specific organ sound. I'm just looking to throw together the building blocks and start playing to see what I can come up with.

[anotherjim]

The EHX pedals are digital, and I don't think you can get near it with analogue techniques.

The Hammond (and others) organ tone that the pedals simulate consist of a mixture of the pure fundamental and some harmonics supplied by higher fundamental pitches of the keyboard tone generator.
The harmonics are therefore pitched to the equal tempered scale of the keyboard -  they are not all integer multiples of the fundamental, only the equal harmonics are correct (simply octaves). The higher numbered odd harmonics are progressively further "out of tune" with the integer harmonic.

The EHX pedal is a pitch shifter, so it takes the incoming clean guitar signal, probably partly low pass filtered and adds pitch shifted copies. The amount of shift corresponds to the organ harmonics, which as I have tried to explain, are not all simple integer multiples.

Further than that, the new signal needs levelling out because organ has a simple on-off envelope.
Follow with simulation of the organs vibrato/chorus and finally simulate the twin rotor Leslie speaker the organ sound is closely associated with.

I have to say that the nearest I've heard guitar get to an organ sound by analogue means is the overdriven sound that John Lord of Deep Purple used on his Hammond, because it is very close to an heavily overdriven guitar in the first place, but you have to stick to power chords or it's just a mess.

[pdavis68]

Interesting. Thanks for the details information. I won't pretend to understand all of it, but I get the gist of the harmonics not being simple integer multiples. I'm guessing the tonewheel is what encodes the harmonics in the organ itself.

I have a Hammond M3 in my garage that I plan to strip fairly soon (normally I strip them right when I get them, but I've been recovering from a bout of pneumonia). I normally get rid of the tone wheels, but maybe I'll examine this one and try to get a better handle on how it works. Maybe I can figure out a way to incorporate it into a pedal (much bigger and heavier than your average stompbox, no doubt).

[vigilante397]

My "organ" sound I use is a Fuzz Factory running through a Mooer Pure Octave with two octaves up and down. I owbed a B9 before and the fuzz+octaves isn't as realistic or even close, but it does well enough for onstage for me

[Ben Lyman]

The cheap little Zoom pedals have an ok organ sim. I think it's a combo of octaves (up and down) plus a little compression, some low pass filtering and a vibe/rotary effect

[anotherjim]

The tone wheels provide all the fundamental pitches -  each one is pretty close to sine wave. These feed the key switch stacks which feed the drawbars. Each drawbar (actually an 8 position switched volume control) sets how much of the controlled pitch sounds off each key. The 8' drawbar is considered the base pitch of the note and the rest are its harmonics. This is really additive synthesis. If I only have the 8' and 4' drawbars out, it will play 2 tones - if I press the key for A 440Hz, it will also sound A 880Hz.
I don't want to get into the maths for the odd harmonics, but I just found this which is as good an explanation as any....
http://electricdruid.net/technical-aspects-of-the-hammond-organ/
By our own Tom isn't it?
And I just learned from this that the Hammond isn't quite to equal tempered, but it don't change things much.

Actually, the reason I thought the 5 1/3' drawbar is left of the 8' is because when used together they create a phantom sub octave, so the 5 1/3' sounds lower when you add it to the 8' although it's a 5th higher.

We could, if we had a reliable pitch follower, generate some harmonics from that (they would have to be integer) and at least have a monophonic organ sim for a guitar. It will sound more like a solid state organ than a Hammond. And "Reliable pitch follower" for guitar is very hard to achieve with analogue circuits.

I don't know how you might control a real tone wheel from guitar. With a lot of work, someone could turn it into a midi controlled Hammond  sound module.

[robthequiet]

Primitive pitch detection is doable, e.g. the early Roland or Avatar guitar synths, but fairly complex. I think I would go with a guitar tone at minimum and some tremolo/vibe effect to get a semblance of organ, as a start. Especially with the wound strings in the upper fret range, where the tone loses a lot of complexity.

[blackieNYC]

The sound that says "organ" to me is a blend of two octaves up. Maybe it's the only sound that does that (has the capability of skipping the 1octave and giving you the 2nd, not that the 1 octave can't be in there too.)That and a Slow Gear gave me an awesome organ sound. Then those goddam ehx organ-in-a-box pedals came out.  It takes digi to do it.

[anotherjim]

As it happens, the most popular Hammond setting is 16', 8', & 5 1/3' drawbars fully out and the rest fully in. Known as the 888000000 in drawbar speak.
So that's an octave & a 5th added. Not far off from playing triple stops on a guitar (root/5th/oct).

Funny how the Hammond M series is so unloved, actually reviled in some circles. Given that it was an M series used on the sessions that produced one of greatest organ pop hits ever  - "A whiter shade of pale", it's very strange. It's all down to those "Disciples of Jimmy Smith" who worship the B3 above all others I think. Listen to AWSOP and you won't hear any keyclick which was much reduced in the M's. But in taming the click, it had a duller top-end. Personally, I am annoyed by clonewheels that won't let you turn the key click off, although it would be easy to add in the menu's.

[ashcat_lt]

So that's an octave & a 5th added. Not far off from playing triple stops on a guitar (root/5th/oct).

Well no.  It's an octave and then the fifth above that.  Easiest way to play that is to grab a C chord, drop your pinky on the high E at the third fret, and mute every string other than 1, 2, and 5.  You can slide that around, but you're still going to be limited to monophonic playing.

It may be obvious, but one trick to sounding like an organ is to play things like they were played on an organ.  Definitely don't do things that an organ can't do - like bends and finger vibrato. 

But keyboardists tend to voice their chords a bit differently than we do, and (at least if you look at just one hand) they can't play six notes at a time, nor can they really span much more than an octave.  The standard triad on a keyboard is the lowest three strings of a G or C chord and the "middle three" (starting on the one that's the octave) of an E or A chord, and really that's almost as far as most keyboardists like to stretch most of the time, but they also usually try to move that hand as little as possible, so any inversion you can find inside or very close to that box is fair game.  The 5-1-3 inversion (the other middle three in E or A, or the top three of C or D) is pretty common I think, too, but like if you're playing I IV V, you'd probably play the standard for the I and use inversions to hit the others without moving too far.

Edit to add - I suppose it's worth mentioning also that it's easier for a keyboardist to play close intervals.  We find it pretty tough to play seconds, and even harder to play a semitone doublestop.  We just plain can't play an add2 within a single octave unless we "cheat" with an open string.  I think it's pretty common for them to play a 7 chord as either 5-7-8 or 7-8-3, both of which kind of hurt on guitar.

[ElectricDruid]

I'm assuming to begin with I'd need a VCF, LFO and envelope filter. Would that be enough to get me on the road to it? Am I missing any key components?

Those are the standard components of an analog synth, and the sound you'll get with that would be identifiably "synthy", not "organy".

Many electric organs build up their sound from heavily filtered octave-divided square wave oscillators, pitched high enough to give all the required octaves. If you started with some flip-flops and got an octave down and two octaves down and three octaves down, then heavily filtered them and mixed it all together, you'd get something quite like a 1970's electric organ. A bit of vibrato/chorus would add to the illusion. I have a Yamaha organ that works exactly this way. A Hammond sim is a different thing altogether. The Paia Roctave would be a good starting point. If you could get the pitch up higher so you had harmonics *above* instead of below, that'd be better, but perhaps you just have to play everything pitched up as much as you can if you want it to sound like an organ.

HTH,
Tom

[anotherjim]

There is a trick for Hammond on analogue synth, and it's pretty good. One of my favourite patches on my old Arp Axxe (From the patch book that came with it), and that's a single VCO. Trick is to use the VCF self oscillating & tracking keyboard pitch. With more oscillators, you can build up a more complex drawbar mix, but the VCO + VCF can certainly make the characteristic Hammond "toot".

A good read on the subject, is Gordon Reids (pun!) Synth Secrets articles from Sound-on-sound magazine, currently available on the way back machine,
Starting here...
https://web.archive.org/web/20160405040354/http://www.soundonsound.com/sos/nov03/articles/synthsecrets.htm
All of 'em...
https://web.archive.org/web/20160403115835/http://www.soundonsound.com/sos/allsynthsecrets.htm

What are called Transistor or Combo organs, which you want for Doors/psychedelic/garage kind of thing, are a bit trickier. Their square waves are simple, but the filtering is nothing you can do with a typical VCF. You need non-resonant RC band pass filters with tweaks to give a general low-pass for the smoother "Flute" sine like tones. Then generally high pass for the brasher "String" saw like tones which are really the hallmark sound of the breed. You can find schematics for the main types of these organs, for free, on line. Vox Continental and Farfisa Compact being the popular types so you can see the filter circuits used.

Most of us don't own a proper vintage organ I'm sure, but there are plenty of free VST emulations to play with so you can hear what does what. I'd recommend finding them via somewhere like...
http://www.kvraudio.com/forum/
...'cause some of the free VST links Google finds look a bit dodgy to me.

[George Moore]

 I fired up the rotating speaker effect. A jack, a plug wire and lots of wood sanding made it suitable for placement under the amp.
A convincing swirling effect and finessed muting of arpeggios, plucked notes and sweeps [keyboard ''switches'' turn notes on and off differently than guitar] can get to a fairly close association with 'organ tone'.
Volume pedal is another aspect that can be nailed with guitar.
It might be helpful to id what analog can and can't do, it's possible to 'nail' a particular organ tone on guitar.
Starting with the guitar wave 'picture' of it's output, the waves can be bent, clipped and doubled, shaping them like 'this' or that organ tone gets trickier with analog unless molding toward square wave.