Cthulhinho is a custom built, Arduino based MIDI controller by Matija Kostevc. It was designed to control multiple instruments at once during live performances. Using the buttons on the top panel, you can control 5 separate synthesisers by triggering chords and song sections. Each button can trigger MIDI parts, and one can switch into arpeggiator mode.

Using the analogue-looking rotary encoder, you can cycle through parameters, which are viewed on the 128x64 OLED. To create a sequence, you set up to 6 separate chords by selecting them within the instrument, or playing in the notes with MIDI learn. These chords are mapped to the to top buttons, using the shift modifier button to select chords 5 & 6. Combining the shift button and the rotary encoder results in changing the chord inversions.

Not only can Cthulhinho play chords, but it has a built in arpeggiator too. The arp allows 16 steps for each of the 6 available tracks. letting you set the volume, gate, octave and CC data. All of these MIDI patterns can be added to the sequencer, which allow you to combine chords and arpeggios into a full song.

Using the global settings, you can dig deeper into the playback. Options such as letting you set bassline mode, which outputs a single note of the chord, and adjusting the BPM and pitch are available.

On the connection side, it features DIN MIDI inputs and output ports, along with an 1/8" jack for syncing with external gear, such as a drum machine.

All in all, this is a pretty great machine. the minimal amount of controls are deceiving the complexity of the features available. The full source, schematics and manual are available at the project's website.