Ed Schmidt said, "Another product called Photoscore is also available,
but I don't know how well it works.  I am sure that there are a number
of other programs, and possible free ones on the Internet."

I have Photoscore MIDI Light, which is available as a download (only)
for $24 US.  It has some serious limitations in terms of number of lines
(voices), it gets confused by some rests, repeats, al. fine, etc., and
it does not handle triplets, but it is an impressive product nonetheless.
I consider my $24 well spent.  I do not have justification for buying
their full version at $159.  The company's web site is at
http://www.neuratron.com/photoscore.htm

It will do scans from sheet music, but I use my scanner to create image
files, then cut and paste the repeated sections, etc and take out
lyrics, and otherwise produce my own sheet music image.  The results can
be loaded in Photoscore and a MIDI file generated.  You can then use a
MIDI editor to correct to taste.  I use PG Music's PowerTracks as my
MIDI editor:  http://www.pgmusic.com/powertracks.htm

Wallace Venable