Cthulhu is two MIDI FX modules combined into one plug-in:

Chords Module - One Note Becomes Many

Cthulhu is firstly a chord memorizer and player, allowing you to experiment with creating and reworking chord progressions with single-note presses. Included are over 150 factory chord presets allowing for a near-unlimited amount of possible musical-sounding chord progressions. Import MIDI or 'record' chords straight in, Cthulhu is able to analyze the chords you play and allow for various sorting options (Circle of 5ths, Chromatic, low note, etc) allowing for easy access over your chords!

Arp Module - Transform your chords in new ways

The other half of Cthulhu is a unique pattern-based arpeggiator, allowing incoming notes or chords to be manipulated in various rhythmic ways. The 8 tabs of the stepsequencer allow you to completely reshape the incoming MIDI notes, even a single note fed into the arp can become a unique and rhythmic riff! Even if you have other arpeggio software plug-ins, Cthulhu's arp is unique and powerful with advanced features such as chord-arpeggio mode, ties, duration / velocity sequencing, intelligent transpose, harmony, and more! Every tab of the sequencer can operate on its own length, allowing for evolving polymetric arpeggios. From simple to complex, from chaotic to creating precise arpeggio you imagine in your head!