HARMONY can now do direct MIDI keyboard to score (since 3.2.7), and, of course, export to abc, but only in step-time, i.e. one note at a time, and not polyphonic.

Capturing real-time keyboard input is not very successful whatever software is used, I understand, and why not just capture to a MIDI file, and process that?

By the way, although the normal games port does support MIDI via two spare pins, I understand that the USB games port adaptors do not.

Not sure if you can get it where you are, but in the UK, Maplins stock a book with the circuit for a games port to MIDI adaptor. I think the only special part is the optical isolator called for by the MIDI spec.