Synth Programming

Synth programming

hi I’m not an expert in this, but I’ve found little help on the Internet so I’ve decided to have a go myself. I have various synths as on the synth history page, but for the purposes of this I will base this programming advice on using a Moog Little Phatty. Of course this is applicable to any basic 2 oscillator synth using subtractive synthesis with a low pass filter. I won’t cover the real basic understanding of subtractive synths as I found stuff on this including often the synths manual. But taking the next step in programming is what this is about.

The Phatty’s basic architecture is two oscillators each with a smoothly variable waveform from triangle to saw to square to narrow rectangle. You can alter the volumes of the two oscillators and the octaves of both but just the fine pitch of oscillator two. There is a sync switch to sync oscillator 2 to number 1.

The low pass filter has the standard cutoff, resonance, keyboard amount and envelope amount plus an extra overload. There are two envelopes assigned already to volume and filter.

The modulation section is quite basic but very effective and will feature a lot in this discussion later. You can choose a source, an amount and a destination.

I will be emphasizing more melodic types of synthesized sound and live performance, but might touch on completely beautiful noise aswell.


So starting simple: just have oscillator 1 turned up with a saw or square wave. Put on resonance half way and a middling filter. Adjust plenty of envelope to the filter, make the filter envelope quite percussive (little or no sustain with a fast attack and a slower middling decay. Add a bit of overload if you like and you can get a sound something like a 303 baseline.

Add in the volume of the second oscillator. Different combinations of octaves add some interest. Both the same octave gives a unified sound, then add a touch of detune to oscillator 2 to add movement. Slight will produce a slow sort of phasing characteristic. Increase it to add a faster movement verging into discordant. Play around with the octave of oscillator 2 to further vary the sound. A few octaves apart will make it sound like two sound – a bass with a high line over the top. You can of course tune the two oscillators to other intervals like 5ths to get that Rick Wakeman sort of sound. Altering the combinations of waveforms from the two oscillators will vary the character of the sound aswell. More of this in the modulation section later.

The sync button makes the 2nd oscillator reset every time oscillator 1 cycles. This will make the 2nd oscillator be in tune with the first whatever pitch you give it. Turn off oscillator one if you just want to hear this altered wave. Try different octave settings then adjust the pitch of oscillator two to get these great sync sounds. We’ll look at this more in the modulation section.


The filter section is reasonably straightforward. A few bits you can mess with. A pure sound like the triangle wave won’t get altered much by the low pass filter, as there are few higher harmonics to cut out. Saw tooth is buzzier and the low pass is dramatic with this. Square wave gives a more hollow sound which the low pass alters well. As you put the resonance up higher the whole sound tends to thin a bit. If you want a stronger sound then lower the resonance back down.

If you push the resonance up to full it will self-oscillate like an extra oscillator. With the keyboard amount at 0, this will be the same note across the keyboard. At full (depending on the keyboard) it can actually be in tune with the other oscillators and track properly. mind you if there is any envelope amount turned on, then you’ll get swooping pitch in the shape of the filter envelope. Which I love anyway – very ravey.


The two envelopes are pretty straight forward. Making these very different to each other can produce interesting effects. Such as make a soft pure bass sound by using a saw waveform but having the filter cut down a lot. Have the volume attack quite fast. But then have a really slow attack on the filter. So play quite fast you just get a deep bass, but hold a note and it crescendos into a buzzier sound. Another neat thing I’ve just found. If you do a lead sound or bass with a long release, then you can let the melody ring out, even though you have let go of the note and are adjusting something with both hands, or playing a second keyboard. This only really works with a monophonic keyboard like the little phatty or in mono mode of another synth or all sorts of notes start hanging around and mushing everything up.


So to modulation – the most fun bit to me. Part of the reason why I didn’t like the original Minimoog that much. I always wanted to modulate something and there was little of that on it.

The Little Phatty only has one modulation bus but you can done lots with it.

The first obvious one is probably the most use for normal lead melodies. Direct the LFO with a triangle wave to pitch. Moving the modulation wheel now adds a simple vibrato to the melody. Classic, very nice. So useful that if you use the modulation for something else instead, then you can’t have the vibrato aswell. Can’t have both, unless you use some of the external bits which connect into this Phatty.

Next obvious one is get the LFO to sweep the filter. If this is really slow, then the synth sound slowly brightens and darkens which I love. With this and the previous setting it is great to by hand increase the speed of the LFO, faster and faster, spinning around until the LFO starts becoming an audible note in itself. Fantastic noise. If you randomly flick the LFO from high to low while having it modulate the pitch, then you get these low whooping sounds alternating with intense buzzes. I’m slipping into live performance here – I was going to cover that at the end.

Next rather nice one is to use the LFO to modulate the wave. The classic sound is to start with a square wave for the main oscillators, and use the LFO to push the sound towards the narrow rectangle wave. This is the same as PWM – pulse width modulation.

Instead of using the LFO, you could get the filter envelope to modulate the wave form, producing change in tone through the time envelope which is very musical and natural.

Lets get back to using the sync button. Turn off oscillator one volume to just hear the synced oscillator 2. You can mix the two later. Press the sync button. Make the pitch of oscillator 2 higher then 1 for the best results, but always experiment. Then try using filter envelope as the source and the destination being oscillate two pitch. The filter envelope now sweeps the pitch of oscillator 2. This oscillator is forced into the pitch of oscillator 1 keeping this a playable sound, but its waveform is massively changed. Set the filter envelope to no sustain, instant attack and middling decay, to get the classic sync sound. On the little phatty this will only happen as you roll the modulation wheel.

Just a few more parts to the modulation section and then I’ll get on to performance tweaking. Now is you make oscillator 2 the source of the modulation then this is an audio speed source – very fast – you can’t really hear the separate oscillations happening. Select a destination of filter or pitch and that will alter them at audio speed. This will more likely just alter the waveform into different sounds in a continuous way. Not like the slowly changing nature of an LFO. I’m still only experimenting with these settings. No real idea of what could be done here so try it out and please tell me any hints. With the Little Phatty you can inside the menu system choose noise as the modulation source. This will add a more chaotic nature to the pitch, filter or wave. Please tell me any ideas you have for these bits.


Lastly performance. With the Phatty you can leave certain parameters ready for quite live messing with. I might choose to have the decay ready to alter on the hoof, changing the sound from sustained to choppy. I would normally have the cutoff frequency quickly alterable as moving the filter by hand gives such great expression to a melody. Changing the envelope amount live can be an interesting alternative to changing the cutoff. If you have the sync on, then changing oscillator twos pitch by hand causes lovely movement to the note character. Just even changing the volume of oscillator two can produce interesting variations between each melody line. Suddenly getting fatter or adding in a second octave. With the modulation section you can alter the amount with the wheel really, so leaving the LFO rate for live twiddling seems most fun to me. As above changing that produces great special effects.

For making complete noise – put the resonance up high, maybe add in the sync, have the LFO directed to oscillator 2 pitch or total pitch, then waggle wildly the LFO rate, the oscillator two pitch and the cutoff. I love noise.

Once I’ve published this I would love it if people emailed me new ideas by clicking on contacts at the top. I’ll add your ideas to the bottom with your chosen name or nickname.

peace James

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