MIdrum UC33 G

A bigger MIdrum, based on a UC-33e by Evolution (M-Audio), new version

MIdrum is a rythmmachine outputting midi. A good explanation of the generative principle kan be found in the Manual of Grids.

Just to be absolutely clear: the idea of generative eigendrums is not mine.
I just thankfully use ideas and code by Olivier Gillet of Mutable Instruments.

This version has 6 drum-channels.
The fader sets the Density for a channel (BD), the pot above adds to that a random amount.
The middle row pot scales the velocity for the channel. The top pot selects the midi note number.

The first 3 channels are the same as those in Grids.
The second 3 channels are derived from the first 3 by calculating their density based on the density of the first 3:

  • Density 4 = ( Density 1 + Density 2 ) / 2
  • Density 5 = ( Density 1 + Density 3 ) / 2
  • Density 6 = ( Density 2 + Density 3 ) / 2

The leds on these faders blink as a note is played.

Switch: up sync external, down sync internal
Top Right Pot = Groove: 12 o'clock: straight, turn counterclockwise for 16T, turn clockwise for 8T [updated every quarter note]
Right Pot below: ModWheel
Fader7 = X & Fader8 = Y: select a position on the drummap. [updated every step]
Leds on Faders 7 & 8: visual bar and beat indicator for your non-midi-syncable-bandmate: Bar=7 & Beat=8
Fader9 = Scale overall velocity

Top white pushbutton = Stop: MIDI sync: Stop
Bottom white pushbutton = Start: MIDI sync: Start
Bottom right red pushbutton = Tap: after tapping 4 times a new taptime is calculated. This new taptime will only be implemented after pressing Start once. So, while the MIdrum is running or not, you can tap 4 times to get the new tempo and press play once to update this new tempo.


Power switch selects power source:

  • OFF: dc, about 9V any polarity
  • ON: usb, just power, no midi

Standard midi in and out, no thru, no soft-thru
No midi over usb

I've kept most of the controls board of the uc33 including the 4 onboard cd4051.

The adapter input is standard guitar pedal format accepting anything about 9Vdc any polarity, it even functions at about 9Vac.


MIdrum 2 on YouTube

Code (similar)
MIdrum at Github


This page is presented for my personal enjoyment. I hope this page will also be an inspiration for diy-ers all over the world. This page is not meant to be a manual, so please don't contact me for guidance or support.
Thank you and enjoy.