MIdrum 2 X2 S2

One more MIdrum :)
The drummachine of the Anushri by Mutable Instruments is great. Olivier Gillet later expanded on it with his Grids.
My MIdrum is the concept of these generative drums, translated into a compact midi-drummachine.

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

Compared to my original MIdrum, two things have changed:

  1. This second version is based on Grids (hence the 2).
    • Interpolate between 25 drumpatterns
    • 32nd note step resolution
  2. This version has 6 drum-channels (hence the X2).

Compared to the MIdrum2 X2 this one is smaller: 17 x 9 cm

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 12 faders and pots control channel specific parameters in groups of 2.
The first fader sets the Density for channel 1 (BD), the pot above adds to that a random amount.
The second fader scales the velocity for this first channel. The pot above 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

4bit turning switch to select* Midi channel: 1=1; A = 10; 0 = 16

  1. Led tempo [off / on]
  2. Midi thru [off / on]**
  3. Midi sync int messages(Clock+Start+Stop) thru to Midi-out [off / on]
  4. Midi sync [ext / int]

Top Red pushbutton: reads and *activates the switches above. It also sends CC#120 (All sound off).
Black pushbutton = Stop: MIDI sync: Stop
Grey/white pushbutton = Start: MIDI sync: Start
Bottom 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.

** Midi thru will try to merge incoming midi messages with the generated drums (and clock) and repeat them on the midi out. This will work for simple note on and off messages, but as soon as continous messages are received the internal midi-clock will suffer severely.

Right Pot = Groove: 12 o'clock: straight, turn counterclockwise for 16T, turn clockwise for 8T [updated every quarter note]
The lower pot sends Modwheel (CC#1) [updated at 48 PpQn].
Left fader = X & Right fader = Y: select a position on the drummap. [updated every step]

Led: visual bar and beat indicator for your non-midi-syncable-bandmate: Bar=Red & Beat=Green

The adapter input is standard guitar pedal format accepting anything about 9Vdc any polarity, it even functions at about 9Vac, just make sure the LM7805 doesn't get fingerburning hot (fingerwarming hot is ok).

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.