ZS001 is a MIDI VST Plugin for Mac OS X and Windows. Free to try, €20 to buy.
Place the ZS001 on a MIDI channel in your DAW, such as Ableton Live.
It can generate chords for a chosen key, change any MIDI pattern into one of 60 different keys or detect the key of existing MIDI patterns.
To buy, please send €20 to firstname.lastname@example.org via PayPal.
Watch the sister You Tube videos here. This one explains Key Detection and Correction:
This one explains Integrating ZS001 VST Chord Progression Generator into an existing tune: