We love the Korg Monotron!
Korg themselves have put together a bunch of cool mods (some commercial, some DIY) on a “We love Monotron” page, and have gathered demos of them all together in a video appropriately called… “We love Montron”.
Here are the mods:
#1 Naotron: Adds a switch that gives the ribbon controller a 2-octave range, and a Roland D-beam type light sensor on the top.
#2 Monomodular: Adds patch points and extra controls in an awesome-looking separate unit.
#3 NSQ-10 and modifications: Added functionality to the EG, an expansion port dedicated to a mini analogue sequencer that can control pitch,filter, and other functions.
#4 Monotron X Sequencer: A full step sequencer, featuring tempo, gate, and pitch.
#5 Monotron Glove: Super cool VR-style gloves. The right changes the filter cutoff and pitch and the left controls the gate.
#6 Momotron: LED change to pink, adds a second VCO and soft sync.
#7 Monotroid: Android mobile phone interface.
#8 MonoChuck: Converts the Wii nunchuck into a control device. so you can use the analogue stick and the accelerometer.
#9 Monotron+: A new enclosure, MIDI interface, CV + GATE, LFO and EG expression and switching.
Most of the mods are available for purchase. Here’s the video: