Doug Baker wrote, "I am wanting to know what the general consensus
is regarding the software to use for converting audio recordings into
a MIDI format ... enabling one to manufacture punched music rolls
for a 20-note busker organ."

At present there are a few programs which can translate a melody from
a simple audio file to MIDI, and others which will recognize chord
sequences.  As far as I know, there is nothing which can accurately
convert a good recording to a MIDI file, and the task is extremely
difficult technically, particularly for large band and orchestral
pieces.

There _is_ pretty good software for scanning sheet music to MIDI file,
editing (arranging in) MIDI files, and printing and/or punching rolls
from MIDI files.  There are also systems which can scan rolls to MIDI
files.

As Robbie noted, an arranger must be involved to get any worthwhile
results.  A typical MIDI file will at least have to have the key
changed, and a lot of notes moved about, not to speak of adding the
bouncy bits which are characteristic of grind organ music.  Then there
are the sharps and flats which your 20er organ cannot play.  (You only
have one in the key of F.)

Anyone can learn to arrange organ rolls from MIDI files, but certainly
not instantly.  Some knowledge of music theory will help as well.
20-note organ rolls are difficult because of the very limited scale.
I'm in my second year of self-directed study and I now get decent
results at least half the time.

Wallace Venable