I am not planning to leave Sonar, but am planning to look into Cubase Elements 9 for $99 for doing MIDI editing.
I downloaded and reviewed the manuals and it has most of the MIDI features of Cubase Artist and Pro.
The MIDI features look inspiring for sure!
To start with, it has the Arranger Track and the Chord Track.
The chord functions and other chord features sound very nice. There is the Chord Track, Chord Events, Chord Editor, Chord Assistant – Circle of Fifths visualization, Scale Events, Voicings, Follow Chord Track, Map to Chord Track, Extract Chord Events, Convert Chord Events, Follow Chord Events, etc.
Then the Chord Pads, for an interactive approach to working with chord progressions, integrated with the Chord Assistant. OK, demo coming soon