A 16 step pattern arpeggiator or gator.

The 16 faders set the velocity for each step. The pattern / steps are always running, synced to internal or external midi-clock. So the 16 faders are always the 16 steps of a bar.
The ArpyGator outputs notes only when:

  • notes are received on the input channel
  • the ArpyGator is running / synced
  • the ArpyGator is enabled
  • Velocity scaling is > 0
  • Velocity current step > 0

Work in progress. This version is a proof of concept.

The SlideSwitch top-middle (S R) sets the mode of operation: Arpy / Off / Gator
Each mode has its seperate controls:
Arpy uses Pots L1-5 & C1 and Gator uses R1-5 & C2

Top Left to right

S L (Slide Left) nothing yet, maybe Hold?


  • L1 Shift Octave
  • L2 Arp Pattern (Up, down, pendulum, up&down)
  • L3
  • L4 Groove
  • L5 Velocity

C1 out Output Channel Arpy

SR (Slide RIght) Arpy / Off / Gator


  • R1 Shift Octave
  • R2
  • R3
  • R4 Groove
  • R5 Velocity

C2 out Output Channel Gator

Cin select* Midi input channel: 1=1; A = 10; 0 = 16
Dip4: Dipswitches*:

  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]

Dip: reads and *activates C and Dip4. It also sends CC#120 (All sound off).
Stop: MIDI sync: Stop
Start: MIDI sync: Start
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 notes (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.

To do

Hold (pedal / slide)

Control board
16 Faders
3 switch 4bit
2 Slide switch
11 Pots
1 Dipswitch 4bit
2 two color led
4 buttons

Motherboard (10 x 21 cm)
bridge rectifier
2 4067
1 6n137
Arduino Nano V3.0

ArpyGator on YouTube

Synthforum (Dutch)
Babbel mee



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.