I have used a program called Sharp Eye (see www.visiv.co.uk) which
works reasonably well.  I wouldn't say it is 100% perfect, but it does
most of the hard work.  You would also need an editor to correct the
MIDI file (Sharp Eye doesn't give you that facility, it just produces
a file).  There is a free 30-day trial you can download, and the full
version costs $169 (I'm sure it was less when I bought it 3 years ago).
Complex music with multiple chords can cause problems, but simpler
music works well.
 
John Farmer, UK
Archivist MBSGB