Sundog Song Studio:
Sundog is a powerful combination of chord progression tool and step sequencer. First, you create your own chord progressions - simply by clicking on chord buttons that fit your chosen scale. Then, you use the built-in step sequencers to create harmonic melodies that always fit your chords.
ChordPotion:
Send chords through the ChordPotion MIDI plug-in, and ChordPotion will transform them into new phrases instantly (arps, rhythmic chords, basslines,...). Mix and combine different playing styles with each other to create your own unique recipes. You can export all phrases as standard MIDI files.
MelodicFlow:
MelodicFlow is a MIDI performance plug-in that makes it very easy to play harmonic melodies and basslines right away. Simply send some "reference chords" through MelodicFlow, and MelodicFlow will make sure that the melodies that you play on the upper white notes will always fit these chords.