Hi all,

I've been using the Rob Hordijk Harmonic Oscillator module for several weeks and I have some info & impressions.

Basic info - It's a 5U Dotcom-format oscillator with some unique features and a really distinctive and musical range of sounds. The signal starts as a sine wave, which then gets modulated by two separate voltage-controlled analog waveshaping circuits to create a wide variety of waveforms and sounds.

The first circuit adds odd harmonics, which lets you morph the sine wave into a square wave, but with a somewhat different response than what you would get just by using a filter. The second circuit adds all harmonics, modulating between a down-saw, through a sine, to an up-saw. Or actually, the center position could be a sine, or a square wave, or something in between. The center position is basically whatever the first circuit is currently doing to the waveform.

This arrangement lets you do all sorts of filter-y effects without using a filter, or you can create a big fat mixed square+saw wave, or you can create a waveform with a very animated timbre that sounds somewhat saw-ish, but that has a really strong sweeping effect imparted on the saw wave that sounds kinda like flanging or pulse width modulation.

It also has a built-in VCA, which can be used simply to control the level, like other VCAs, or you can patch the VCA out to one of the harmonic modulation inputs to make the module's waveform modulate itself under control of the VCA.... As you can see, it's not your basic vanilla oscillator.

And it just plain sounds really good. The way the waveform shifts from one shape to another just has a really organic musical quality to it. You don't have to process or EQ the heck out of it to get it to sound 'right'.

Here's an illustration of the panel controls. I'll post some clips soon.

Hmm. Something wrong with the jpg attachment. Ok, here's a photo. It's the module on the left.

OK, this first clip uses the Harmonic Oscillator for a classic monosynth lead sound with a twist. At the start of the clip, the waveform is a soft tone, using an LFO to modulate the waveform between a soft, rounded square/sine and a mellow sine/saw. Then the modulation depth increases, creating a brighter tone that sounds like a sawtooth, but with a flang-y effect or maybe a sort of pulse width modulation effect on the saw wave.

There is NO filter used in this clip. It's just ONE oscillator through a VCA, with a bit of delay.

Great to hear such an animated tone from just one oscillator. It has shades of PWM in there - and it'd generally take two oscillators, tuned within a hair of eachother, to create the flanging-like sounds.

Thanks for the demo!

Here'sa different type of sound from the Harmonic Oscillator. A simple random arpeggio is playing, and the osc starts out with a sine wave. A few quick knob twists show how it changes from sine to square and from sine to saw and from square-ish to saw-ish to PWM-ish using manual controls.

Then at about the 30 second mark I start increasing the harmonic modulation depth controls, and I'm using a couple of audio-rate oscs tuned to different intervals to modulate the wave shapes - one for the odd harmonics, one for the 'all harmonics' input. This makes a really complex sound somewhat like a ring modulator, but with more motion and constant changes. There's also some LFOs mixed in with these audio rate oscs so you still get that PWM or flanger-ish effect fading in and out.

There's some syncopated delay to make the arpeggio more interesting, but again there is NO filter and only ONE Harmonic Oscillator. The other oscs are just modulation sources. Quite a big and complex sound from one oscillator.

Here's another lead sound. The timbre shifting is more subtle, with slightly different modulation routing than the first lead sound clip. This one uses the Harmonic Oscillator's own output to modulate the wave shapes, but it first passes the signal through a couple of VCAs controlled by two different slow LFOs to vary the modulation depth. One of these audio-rate mod signals controls the odd harmonics, the other controls the "all" harmonics, so the harmonic content is changing in subtle but complex ways. Especially during the low note at the end you can hear how this creates some slow random changes in the sound.

That sounds really epic . Cool demo .

Thanks!

Here's one more. This one is a simple drone. It uses self-modulation along with audio-rate modulation from another osc for the wave shaping, mixed with some LFOs for some complex sound shaping. There is some chorus and delay, but again there is no filter and only one Harmonic Oscillator. The second oscillator is only used as a modulation source. You can get a pretty big sound out of this thing!

very nice Dave!

Absolutely majestic sounds... never heard about Hordijk...so I got som googling to do now

Extensive Salivation

Awesome sounds Dave, thanks!

awesome demo

this is one of the reasons i love modular synthesis so much.

you don't have to depend on the big companies to release something with a few features you like and a whole bunch of bloat you don't want to pay for

and innovation can come from anyone's basement.

what a killer oscillator. thx for taking the time to show us what it sounds like