Is there anything like Photoscore available?
http://www.neuratron.com/photoscore.htm. It seems to me that although the character recognition is quite good, it doesn't really use other information. For example, I just scanned in something in which the sharp symbol was "recognised" as an extra note. Clearly the sum of the values for the bar was then incorrect which it flagged up for me to correct. But a better approach would be something Bayesian which would give scores to various guesses (that the symbol was a sharp or that the symbol is a not) and then pick something which fits the bar. Another example is a dot over the top of a note indicating staccato; Photoscore sometimes "recognises" this dot as making the preceding note dotted and again the values then don't add up for the bar.