The Automatic Chord AlgoriThm

AutoCAT is a VST plugin for generating MIDI chords based on an input stream of MIDI notes. It works in real time, providing some accompaniment while you play, however, the algorithm can only react to past notes, so it will always take one bar to catch up to you. For best results, you can feed into the plugin the midi messages used for your melody, one bar early.

AutoCAT synchronizes itself with its host, playing one chord per bar. Furthermore, AutoCAT has a number of parameters that control how it behaves.

AutoCAT is OpenSource, you can check out its code here.

Parameters

• Velocity: MIDI Velocity of the played notes. I also recommend combining the plugin with some MIDI humanizer plugin to get some variation in the velocity.
• Density: Maximum number of notes per chord. The algorithm never repeats the same note class, so the chord can end up with less notes than what is set here for some slow melodies.
• Staccato: Note duration, as a ratio of the measure duration. Larger values result in short stabs, while longer values get more legato pads.
• Octave: The base octave for the notes, chord notes can be in this octave and the octave above the one selected.
• Discard Notes: If this is on, the chords will replace the incoming notes, if it's off, the chords are added to the incoming notes.
• Synch Play: This garantees that chords always play at the begining of a measure. However, chords will only play while the host is playing. Generaly, you'll want this on for real-time comping and off when working on a composition.

Demo

Download

To install, simply unzip the Autocat.vst3 into your VST folder.