'HARMONY is a magnificant abc & MUSIC editor and player which provides almost all the facilities you will ever need in a Music package'

Well, maybe not quite, but it has some unique and useful facilities.
The original objective was to add chords (automatically) to a tune, but it has grown a long way from that.

It now provides import of tunes in various formats, including MIDI and abc.

It displays, transposes, adds chords and harmony lines, edits, plays and also writes MIDI output.

It can generate random tunes in a selection of styles (Jigs, reels), and can transform a tune into a round or play it backwards, to assist creativity.

It understands repeats and 'part specifications' such as A (AB)*2 (AC)*2

It can import and display multiple verses of aligned lyrics, in one or more voices.

And plenty more as well!
Thanks for asking, and it costs nothing to download and try it.
Find it at http://www.greenhedges.com