The Dual Osc M-odule

Review by b3nsf

The Dual Osc m-odule is very powerful, you can use it straight up as a bank of oscillators and sub-osc, or as a ticking and counting timing device! The function blocks are: NTO, PCO, ÷N COMP, and MIX PRO. Please listen to a demo I put together using only the Dual Osc M-odule and nothing else. Enjoy, and please go buy a Dual Osc M-odule from Rex Probe!

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The NTO (New Timbral Oscillator) was born in and got its name from the TONTO (The Original New Timbral Orchestra) mega-synth, owned by Malcolm Cecil used by many great synthesists including Stevie Wonder. The NTO’s were originally a replacement for the Moog oscillators in the TONTO synth because they were more stable, so the first Serge NTO’s had Moog faceplates!

The NTO’s most notable features are the variable wave shape, the voltage controllable FM amount, and the voltage controllable portamento amount. Variable wave shape is one of those features that just shines. You can get the most beautiful and complex patches by modulating the VC wave and routing the variable wave output as you would a normal oscillator. This way the character changes at the root level of your patch and everything after it becomes more interesting. The VC FM is another extremely interesting way to add complexity and timbral changes, input an oscillator signal into the IN FM and an LFO into the VC FM to get a nice tone that gets more vibrant and evolving as the LFO rolls through the frequency modulation! The VC PORT controls how much portamento is used from the IN PORTAMENTO jack, the portamento feature is not subtle, but it glides nicely back down to normal so a trigger will do nice fluttery effects!


The PCO, while lacking the some voltage control features found on the NTO, is great at supporting it and because they both track perfectly together, these two are the perfect pair! Together they form an amazing team and the NTO would be weak without its little brother to supply sync, linear, exponential and variable frequency modulation. The PCO’s SINE output sounds incredibly fat by itself, but with two sine waves mixed together you have some real grade A beefiness! One “old-school” trick is to plug the two sine outputs into each other’s FM inputs, and sweep the frequency of the oscillators at the same time for a classic Doctor Who sound effect. The SYNC input requires a SAW wave and will grab and reset the oscillator based on that saw, resulting in a “soft sync” that staircases as it tracks, and sounds pretty neat! Rex says a cool thing to do with your sync signal (saw) is to run it through a vca with some volume modulation for a neat sounding on/off syncing feeling. The RANGE switch can make the PCO very slow indeed, essentially making it an LFO/bass module. The PCO also has two inputs for 1 volt/octave exponential tracking and one variable tracking input.


Ah, the ÷N COMP, easily one of my favorite function blocks. This thing should be called the “Sub-Oscillation, Pulse Width Modulation and Snare Trigger Generator”. It can be used in lots of ways! The IN + and IN – compare the voltages and output a squared version of the difference. For example if you patch a sine wave oscillator signal into the IN + and an LFO into the IN – you get a PWM square wave with the LFO sweeping its width, a real barn burner of a sound sure to blow away what you had thought PWM sounds like, this ain’t no Roland, kids! If you plug a second oscillator into the IN – instead of an LFO you get a real chewy version of them together, not unlike a Harley Davidson with a jack-hammer in the side car, and a helicopter flying overhead all at the same time!! Needless to say you can damage every part of your ear with this patch, even at low volumes… For really fun sub-osc sound use the divided output at the top and dial your octaves down with the ÷by knob, its adds girth and bass, and it has its own stair-casing effect when you sweep it.

The real fun is when you use the ÷by section for trigger pulses, this is perfect for drum machine patches because if you divide by 8 or 4 you have a logical snare trigger, with this it is entirely possible to make a “beat” with no sequencer, just function blocks doing their thing, holding down that rhythm!

The ÷N COMP is also a crude and bizarre feedback oscillator with one cable from the lower OUT jack back into its IN -. You have to turn the bottom knob towards the plus side till you hear the shreiking sound and then it’s anybody’s guess what you want to do with its shrill, stair-stepping sound madness! Try it once and never do it again! Your cats will hate you, forever.

Just a quick mention, the STEP OUT sends an upward staircase of voltage corresponding with what current step the divider is on. And the VC IN controls how much to divide by, scaled by the knob. So if you scaled your LFO voltage before going into the VC IN, you could theoretically get a funky trigger that hits on beat and off beat– something to try once you get the funk machine revv’ed up!


The MIX PRO does a bunch more than just “mix”. Channels 1 and 2 do standard additive mixing, but the third has the ability to subtract from the other two with its invertible, positive through negative volume knob. This is a great feature and can be used to sculpt a new waveform from two otherwise tame waves. In fact if two oscillators with the same waveform and the same exact frequency are both added and subtracted (example: chan 1 and 3 set to fully negative) in this way, you hear nothing at all! They cancel each other out. This is really great if they are slightly out of tune, then you get a lovely tremolo effect.

Mix pro also has a positive through negative offset at the top, this is really essential for getting just the right amount of modulation once you’ve subtracted out with channel 3’s voltage. You can create the most interesting modulation sources by mixing 3 LFO’s and sending the result to … well the variable wave-shape of the NTO or just about anything, for that matter! Before I got my Dual Osc M-odule, I thought my Serge would always bubble and cycle, but the Mix Pro has opened my eyes to the “landscape” of rolling hills and modulation valleys that are possible!

That’s not all, folks! The invertible channel 3 can open the door to feedback within your Serge, and this is an endless source of unexpected sounds as you mix the original signal with the feedback signal and they add instead of canceling, incorporating your favorite Serge function block in between (wilson delay, Q filter, wave multiply ) and you have instant certified madness! It’s no wonder that people with 3 channel mixers in their Serge have the most fun, they are all using ridiculous amounts of feedback!!

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Serge Modular Shop Panels and M-odules (including the "Dual Osc" M-odule) are currently manufactured by Sound Transform Systems (262) 367-3030.

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