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Convert MP3 to MIDI on your device

Turn a sung, hummed, whistled or played melody, one note at a time, into a MIDI file.

Transcription 

    

    
The table lists each note with its start, length, offset from equal temperament in cents and confidence, unsteady notes included, so you can see which ones to check against the recording.


    

      
    


    

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One melody line from a mono copy resampled to 22,050 Hz. Silence and flagged polyphony are refused; drums and speech can be refused, but a clear single voice can pass. Checks can miss chords or mixes. A recording over five minutes is refused by name. Takes .wav, .wave, .mp3, .m4a, .aac, .ogg, .oga, .opus, .flac, .aif, .aiff and .weba.


    

    
  


  

    
How this transcriber works

  

    
Your browser reads the file into memory and decodes its audio. The page mixes it to one channel at 22,050 samples per second, as the readout shows, and tracks pitches between C2 and about D6 (65–1,200 Hz). It analyses overlapping frames of about a tenth of a second, spaced closely enough that a note lasting a sixteenth of a second appears in several of them.

    
YIN estimates a frequency for each frame by finding where the waveform repeats and refining that interval to a fraction of a sample. The note confidence comes from how closely that repeat matches within accepted frames, averaged over the note; it is not a measure of pitch variation between frames. A second check measures the energy in bins near the estimated pitch and the seven multiples above it, the first eight harmonics, and a frame counts as a note only when at least 35% of that harmonic energy sits at the estimated fundamental. That is the check that lets the tool refuse a chord whose combined waveform repeats like a single note.

    
Frames are grouped into notes where the rounded pitch holds steady and passes the harmonic test, and a note under 60 ms is dropped. If fewer than half the frames with a pitch estimate pass the periodicity and harmonic checks, the whole file is refused and nothing is exported. Mixtures, unstable sound and sound outside the tracked band can cause that refusal, and the checks do not catch every chord or mix. A kick drum’s falling pitch usually fails the periodicity check, but a clear single voice can pass and is written as the notes it sang. Notes are rounded to semitones, velocity comes from the measured level, and times are rounded to MIDI ticks, 480 to a quarter note at 120 BPM; that tempo is only a timebase, with no beat grid fitted. The cents offsets stay in the table and are not carried into the file as pitch bend. The MIDI keeps no timbre, words or chord arrangement from the source.

  

  


  

    
Frequently asked questions

  

    

      Is my audio uploaded anywhere?
      
No. The browser reads and decodes the audio, and the pitch tracking, the harmonic check and the MIDI writing run in this tab. The page downloads no analysis library. The meter counts resource-timing entries from the first file read; it does not see earlier page requests or every network channel. The methodology page explains this and describes an offline test.

    

    

      Why does it refuse chords?
      
Because a chord can make a pitch tracker report a note nobody played. A triad such as C-E-G has frequency ratios near 4:5:6, so the combined wave repeats at a fundamental two octaves below its lowest note, and a tracker can lock onto that missing pitch. This tool checks how the signal’s energy sits relative to the detected pitch and refuses a passage that does not look like one melodic voice.

    

    

      What should I feed it?
      
One clean melodic line with no backing: a sung, hummed or whistled tune, or a solo instrument between C2 and about D6. There is no speech detector, and a clear single voice can pass, so speech that passes comes out as pitched notes. After converting, check the note table, then open the MIDI in a MIDI player or editor and compare it with the original recording. This page does not play either file.

    

    

      How accurate is it?
      
The table shows where to look: for each note it prints how far the pitch sat from equal temperament, in cents, and how cleanly the waveform repeated. Very short notes, strong vibrato and unstable pitch can cause errors, and a pitch that crosses a semitone boundary can be split into two notes. The MIDI output uses rounded note pitches without encoding those cents offsets. That is this tool’s choice: MIDI files can carry pitch bends.

    

    

      What is in the MIDI file?
      
A format 0 MIDI file with one track: a tempo event, a note-on and note-off pair for each transcribed note, and an end-of-track marker. Standard MIDI software can read this structure, though compatibility depends on the application. The tempo is set to 120 BPM with 480 ticks per quarter note, about a millisecond per tick. Each note’s start and end are measured in seconds and written to the nearest tick, with no bars, time signature or beat fitting, so changing the tempo in your MIDI editor changes when the notes play.

    

  

  


  

    
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