Optical music recognition, or OMR, does for sheet music what text OCR does for documents, but the job is harder. Music is two-dimensional: pitch depends on vertical position on the staff, rhythm depends on note shapes, flags and beams, and a single accidental changes every later note in the bar.
A recognizer first finds the staff lines and groups them into systems. Then it detects symbols: note heads, stems, beams, rests, clefs, key and time signatures, accidentals, ties and dots. Finally it rebuilds the meaning: which notes form a chord, which voice they belong to, how long each one lasts, and where each bar starts and ends.
The result is written out as MusicXML, a full description of the score. From there it is a short step to MIDI for playback, or to a freshly engraved PDF.
MusicXML or MIDI: which one do you need?
MusicXML keeps the notation. It knows that a note is an F♯ and not a G♭, that it sits in the alto voice of the upper staff, that it is tied over the bar line. Open it in MuseScore, Dorico, Sibelius or Finale and you can keep editing the score as a score.
MIDI keeps the performance: pitch, timing and loudness, with no idea of spelling, staves or beams. Use it for playback, for practice tracks, or to drive a virtual instrument in your DAW. If you want both, export both; they come from the same recognized score.
Printed, scanned, photographed or handwritten
The cleanest input is a PDF exported straight from notation software. Every symbol is sharp and consistent, and nothing is skewed. Next comes a good flatbed scan of a printed page at 300 dpi.
Phone photos work when the page is flat and evenly lit, but curl, shadows and perspective all cost accuracy. If photos are your main source, the Sheet Music Scanner lets you straighten the page and adjust the corners before recognition.
Handwritten music is the hard case. Every copyist draws note heads, stems and beams differently, and recognition models trained on engraved music struggle with that. We do not recommend paying to scan handwritten pages.
What to check after a scan
Listen through once with the score in view. Most errors are easy to hear: a wrong accidental, a missing tie, a triplet read as straight eighths, or a rest in the wrong voice. Hover the bar to replay it and fix the detail in your notation app.
Pay extra attention to repeats, first and second endings and D.S. or D.C. markings, because they change the playback order. Lyrics, chord symbols and expression text may not come through, so check them before you print.