Math Perc 1 - formula based additive percussion

Math Perc 1

This unit is based on the inharmonic series of certain types of percussion as explored into this article.
I used the formula fn = a (n+1/2)2 f1 where “n” is the node number (the partial number, from 2 to 7), “a” is a constant based on the shape of the instrument and f is the fundamental frequency.
This implementation uses 8 partials (1 fundamental + 7 [in]harmonics).
I recreated the formula operations with vca’s and mixers(multiplication, division, addition, subtraction, elevate to the power of…). I think the routing options of the er-301 combined with the digital precision of the units are great for this kind of fake analog math! Of course something like this would only require a simple line of code, but there’s a certain fascination in trying to recreate it with vca’s :slight_smile:
I’m not really sure i got the math right so if someone could check it i’d be grateful.
It uses 8 sine oscillators so it is definitely an additive take on percussion synthesis.
I really like the results!!!



  • gate: this triggers the ADSR controlling the amplitude VCA at the end of the synthesis chain.
  • f: this sets the frequency of the fundamental.all partials will then be related to this f via the formula.
  • shape: control for the “a” parameter of the formula setting the shape of the instrument
  • vca: inside it you’ll find the ADSR controlling the amplitude VCA. you can delete it and swap it for your own external envelope (i suggest function generators with snappy, exponential slopes like maths, rampage, falistri, dusg…)

cpu : about 40%
firmware : v0.4.11 or later
requires : no dependencies
tips : i prefer other envelopes, really snappy ones like maths\function\falistri. you can open the vca control and you’ll find the ADSR, delete it and patch your external envelope generator here. also, there’s plenty of CPU left to add at least 4 other harmonics, you just have to copy\paste the last mixer channel (p7), go inside, find the mixer channel named “n” and change its number to 8, then in the next one to 9 and so on.

Math Perc 1.unit (119.2 KB)


i had fun with this! let me know what you think!


Lovely sound!

thanks! just updated it! now the shape of the percussion instrument can be set with the “shape” control.
also the vca is explicit now so you can easily swap internal adsr with something else!

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Sounds cool. Need to spend some time catching up on all these new custom units!

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thanks Joe :slight_smile:
and i need to start learning lua!!! i have so many ideas right now…

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Cool! Sounds good…!

Heh, you will have a ball in the middle layer, it should come with a warning though, it’s erm, quite addictive :slight_smile:

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ehhehehee :slight_smile: pretty sure of that !

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Apparently I have just written a 300+ line bespoke unit, I am not entirely sure how this happened - did someone mention it was dinner time?


:open_mouth: 4char of amazement!

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Nice! Mine really can’t get delivered soon enough :smiley:

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another example:


wow very cool, can’t wait to try this one out

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