When I first started with Notation Composer it would take me a couple days to "fix up" a MIDI to be usable. Now it takes about 15 minutes each. So even if I did it fresh today it would take 40 hours to build these. And that doesn't include the time finding a good midi to start with.
95% of these tunes come from
http://abcnotation.com/
What I have done beyond just loading in the MIDI and saving is:
All repeated looping removed from the MIDI and reentered as Music Notation with repeat symbols that Notation Software obeys. Most tunes will fit on one modest size laptop screen in a good size font. NO JUMPing around as it plays which makes me lose my place !!
All tunes loop the entire song 3 times using Repeat instructions. Royal pain in the butt to add to each tune.
All tunes have a nice count in. So you are on the beat when the melody starts.
All tunes have pickup measure properly aligned (a problem when importing a lot of MIDI's).
Most all tunes have chords labeled.
Most all tunes have some sort of chorded instrument as well as a melody.
You can find them all here
http://softronix.com/fiddle/Music/Notation/
Enjoy