Forum was searched for 'ocr' and 'recognition'
I'd like to propose this idea for the Gimp:
a paper sheetmusic cleaner
it probably consists in a series of tasks, to start of with;
to scan in music, straighten or transform it (perspective) according to staff lines, crop, despeckle, remove unknown shapes (with the ability to put back), that would require a bit "opposite" OCR though with a shape collector, and optimum 2bit black and white translation.
If you like this, feel free to do so. I hope you get something out of it, and I hope it is a great use for the public.
Thanks for letting me speak :)