Custom unit attempt — scannable harmonic oscillator

! This thread is deprecated, please visit this one for an updated version


I received a 301 a couple days ago and of course I’m in complete awe. Barely beginning to scratch the surface but here’s my first attempt at a custom unit — scannable harmonic oscillator inspired by a well known Eurorack harmonic oscillator, built around Sine Oscs and the brilliant Bump Scanner unit. Controls should be pretty self explanatory — ‘center’ scans through harmonics, ‘bwidth’ sets the width of each frequency band (bands have to overlap for smooth scanning), ‘xfade’ controls Bump Scanner’s ‘fade’ parameter, ‘fdbk’ controls Sine Oscs ‘feedback’ parameter and individual harmonics level faders control… well, individual harmonics levels.

Processor load should be around 33%.

Thanks Neil Parfitt and Joe Filbrun for your incredible videos!

scan-harm-v1.lua (186.1 KB)

(demo has some Strymon Big Sky on it)


scan-harm-v2.lua (191.2 KB)

  • this is the last version for v0.3.x
  • added FM (via ‘fm in’ local control — assign audio rate signal!)
  • added FM amount (exponential envelope from Maths works great)
  • small fixes


scan-harm-osc-v3.unit (154.9 KB)

  • works in 0.4.x / 0.5.x
  • small fixes

(with FM from furthrrr and a touch of the great Joe’s Bespoke Flanger and Strymon Big Sky)

(controlled with teletype via i2c and just friends [geode] + a bit of spread delay in the 301)



Demo sounds great! Looking forward to trying it out.


Echoing @Joe here: demo sounds excellent! Thanks for sharing.



1 Like

Got my 301 a few days ago. I haven’t been able to load anyone’s chains. I had put this down to version mismatches. But it must be user error. I assume this is compatible with 3.18?

  1. I highlight where it says “OUT 1” or “OUT 1 + OUT 2”.
  2. I select Load, navigate to the file and press ENTER.
  3. The 301 puts up a dialog box which seems to be building the Chain.
  4. Nothing is in the chain though.

What am I doing wrong? I would really like to learn from other people’s chains at this point!

EDIT: Importantly, I can save and load my own chains!

1 Like

hey. this is not a chain preset, this is a custom unit preset. you put it in presets/units/custom-unit directory.
to insert it into your patch you have to insert a custom unit, then click on its header’s soft button, then select ‘Load preset’.

Aha - Thanks @joe_biomassa ! I must have missed this important bit of info somewhere. Just got it working. Sounds lovely right off the bat!

EDIT: This is really useful to me - both because it sounds really great and I had been looking into the Verbos harmonic oscillator and the new Frap Tools Fumana. But also because it is relatively simple to deconstruct - having only a couple of layers - and everything is labelled - so it works well as a teaching tool too! I hadn’t started looking at Custom Units as I have been methodically making my way down the list of Units! Thanks again.


Glad you like it! Yes, it’s super simple, my first! I borrowed a Verbos a couple weeks ago and used it for a week, I wanted to play with it for a long time but in person it was even better than I thought.

1 Like

This one of the delights of the ER-301 for me.

Thanks @joe_biomassa look forward to trying it.


Had a little fun using this custom unit to stress test some firmware tweaks…:headphones: Fiiiiivvveeee…:laughing:

Units used:

  • scan-harm-v1 Custom Unit
  • Grain Stretch
  • Freeverb
  • Clocked Delay
  • Limiter
  • Mixer
  • Fixed HPF

whoa. wow. thank you! and the test sounds great.

Brian freaking rocks. May we have the landslide?

Interesting. Using the 48khz firmware I can run two copies of this unit, the processor load goes up to 80% but playback is perfect, no crackles. On 96khz only one copy goes at about 62% and crackles are constant. Anybody else noticed anything like that?

It is expected. 48kHz is more than twice as efficient than running at 96kHz because they are both running the same buffer sizes.

Good to know. Thanks!

I really like how audio is prioritized in the system — at 48kHz under very heavy load saving a quicksave or even drawing interface becomes sometimes a bit sluggish but audio playback remains pristine.

that was something i really needed,
thank you !


hey, i’m happy you find it useful!

added FM!


Sounds great! Thanks for sharing.

1 Like