Polyphonic Audio to MIDI VST converter (free would be best!)

I've tried Melodyne DNA and it's honestly not that great for that kind of thing either, it takes a LOT of tweaking to get something good. Transcribing polyphonic music is great ear training though!

Have you lost the ability to play the parts again?

Could be! The original post was 13 years ago :D

Use chordino for chord recognition. Better than nothing.