Optical music recognition online: from a picture of the notes to sound
Optical music recognition (OMR) – sheet music OCR – does for a page of music what text recognition does for a printed page: software looks at a picture of the score and works out the notes, rhythms, chord symbols and signs on it, so that a computer can play it. That is what Duly Noted does, online: upload a PDF or photograph the page, and a couple of minutes later it plays in your browser. This guide explains how recognition works, where it goes wrong, and how to give it the best possible start.
Try it on your sheet music – first piece free
What OMR does
An OMR program works through a page in roughly four steps:
- Finding the staves. It locates the five-line staves, groups them into systems (the treble and bass staff of a piano part belong together) and finds the bar lines that divide them into bars.
- Recognising the symbols. Noteheads, stems, beams and flags, rests, dots, accidentals, clefs, key and time signatures, ties, tuplets – each has to be found and told apart from its neighbours.
- Reading the text. Chord symbols such as F#m7♭5, tempo marks, and the words that steer the performance: D.S. al Coda, To Coda, Fine.
- Putting it together. The symbols become music: which notes sound at the same time, how long each one lasts, and which voice it belongs to. The result is usually saved as MusicXML (for notation programs) or MIDI (for playback).
Why sheet music is hard to read for a computer
Text runs in a line. Music is two-dimensional: notes of a chord are stacked on top of each other, two voices share one staff, a beam joins notes across half a bar and a slur arcs over a whole phrase. Small things carry a lot of meaning, too:
- A missed dot or an unmarked triplet makes a bar too long, and every note after it lands in the wrong place.
- A missed accidental changes one note; a missed key signature changes all of them.
- Chord symbols are often printed in handwriting-style fonts that ordinary text recognition stumbles on.
- Photos add perspective, curved pages, shadows and blur – and scanned pages can be faint, skewed or noisy.
How Duly Noted reads sheet music
Duly Noted is built on Audiveris, the open-source OMR engine, with its own layers on top:
- Text recognition over the whole page and the band above each system, to find chord symbols and road-map words like D.S. al Coda, To Coda and Fine.
- Image matching for the segno and coda signs, which general-purpose recognition often misses.
- Checks and corrections for the mistakes OMR engines typically make: missed or extra bar lines, lost final bars, endings that cannot be right, triplets printed without a 3.
- A playing-order solver that matches repeat signs like brackets, counts the passes through each ending and takes D.S. and D.C. jumps the way musicians do.
The result plays straight away in your browser: the melody, chords voiced from the chord symbols and a bass line, as separate voices you can mute. Whatever came out wrong in the chord symbols or the road map, you can correct by clicking the bar – the playing order and the sound update at once.
The playing order, too
Recognising every note correctly is still not enough to play a piece. Sheet music is rarely played from the first bar to the last. Repeat signs send you back, first and second endings change what you play on each pass, and D.S. al Coda or D.C. al Fine make you jump back and then skip ahead or stop. Miss one bracket over an ending, and the whole piece is played in the wrong order even if every note is right.
So Duly Noted reads the road map as part of the recognition, and plays the piece in that order. To brush up on the signs themselves, read Repeats, endings, D.S. al Coda and D.C. al Fine, with the playing order for each example.
PDF, photo or MusicXML?
| Source | How well it reads |
|---|---|
| MusicXML | Exact – no recognition needed. Export it from MuseScore, Sibelius, Finale or Dorico if you have the original file. |
| PDF from a notation program | The best image source: sharp, straight and clean. |
| Scanned PDF | Good at 300 dpi or more, in greyscale or black and white. |
| Photo | Works well in good light, held straight above the page. The camera scanner in the app helps you get there. |
| Handwritten music | Much less reliable. Neat, printed-looking handwriting has a chance; quick sketches rarely do. |
Tips for a scan or photo that reads well
- Start from a clean copy. Faded print, copies of copies and pencil markings on the staff can be read as notes or signs. If you have a cleaner original, use that one.
- Lay the page flat. Press a book open so the lines near the spine are not curved.
- Shoot from straight above and let the page fill the picture, with all four corners in view.
- Use even light. Daylight beats a desk lamp; watch out for the shadow of your phone or hand.
- Keep still until it is sharp. Blurred noteheads are the most common source of errors. The scanner in Duly Noted waits until the picture is still and in focus before it takes it.
- One page per picture. Several pages of the same piece can go into one upload.
- Scanners: 300 dpi. Higher rarely helps; lower loses dots, ties and small accidentals.
If a passage keeps coming out wrong, try a cleaner source before anything else – a sharper photo or the publisher's PDF fixes more than any setting.
What to expect
Clean printed lead sheets and single-line parts read very well. Handwritten parts are not read yet; dense piano music and very small print are harder, for every OMR program. In Duly Noted you can correct the chord symbols and the road map – repeats, endings, segno, coda and jumps – bar by bar, and the corrections are kept. The notes themselves cannot be edited yet.
Common questions
Is OMR the same as transcribing a recording?
No. Audio transcription listens to a recording and guesses the notes. OMR reads a picture of written music, so it knows the notes the composer or arranger actually wrote.
What does OMR produce?
Usually MusicXML for notation programs and MIDI for playback. Duly Noted plays the result directly in the browser, and you can also download it as a MIDI file.
Can I try it for free?
Yes. Your first piece of up to 4 pages is free, with no card needed – see pricing.