VELOCITY OUTPUT CHECK
This converter writes a velocity value for each detected MIDI note, but it estimates that value from the audio level of the accepted note frames. It does not recover how hard a performer struck a key, and the same source may sound different when played through another instrument. Convert a clear melody below, download the .mid file, and inspect its note velocities in a MIDI editor before treating them as musical dynamics.
PROCESS ON THIS DEVICE
Use a clear single-note phrase. The preview shows pitch and timing; download the .mid file to inspect velocity values in a MIDI editor.
INPUT MP3 / WAV / M4A / FLAC / OGG → OUTPUT .MID
or click to choose audio from your device
MP3, WAV, M4A, FLAC, or OGG · one file · up to 50 MB / 5 minutesRESULT
Your audio stays on your device. All processing happens in this browser. No file is uploaded to a server.
THIS TOOL'S CODE
For each accepted note, the script averages the RMS of its detected frames. It then rounds 42 + averageRms × 430 and clamps the result between 35 and 118. The number is written with that note's MIDI note-on event. This is a site-specific mapping, not a universal audio-to-velocity formula.
IMPORTANT LIMIT
The writer creates one velocity value when each note begins. It does not write a changing volume envelope within the note. A louder recording level can also arise from microphone distance, gain, compression, or mixing rather than a harder performance.
| Illustrative average frame RMS | Code calculation | Written velocity | What it does not prove |
|---|---|---|---|
| 0.01 | round(42 + 0.01 × 430) | 46 | How hard a key was pressed |
| 0.05 | round(42 + 0.05 × 430) | 64 | The source was musically mezzo-forte |
| 0.10 | round(42 + 0.10 × 430) | 85 | Identical volume on every instrument |
| 0.20 | round(42 + 0.20 × 430), then cap | 118 | More loudness detail beyond the cap |
These are arithmetic examples derived from this site's current source code, not measurements of user recordings or promised conversion results. A note must first pass pitch detection and the Minimum note filter.
TRY THIS
Use a short isolated melody with two steady notes of the same pitch but different recorded levels. Keep browser controls unchanged. Export once and inspect each note-on velocity in a MIDI editor. If a quieter note disappears, lower the silence threshold carefully and compare again; do not interpret a missing note as velocity zero.
AFTER EXPORT
Import the MIDI into one instrument track, keep that instrument and its settings fixed, then compare note velocities. To improve musical dynamics, edit the velocities by ear against the original audio. For a changing level within a sustained note, edit the appropriate expression or volume automation separately.
QUICK ANSWERS
No. An audio recording does not expose the original key-strike value to this converter. This tool estimates one value from accepted audio-frame RMS.
Their measured average levels may be close, or both may hit the mapping's cap. Check the exported event values, not only the piano-roll blocks.
It first decides which frames have detectable pitch. Changing it can change which frames form a note, and therefore the note's average RMS, but it is not a direct velocity slider.
That depends on the instrument and playback settings. Keep the same instrument when comparing exported notes.
Format reference: MIDI Association's MIDI 1.0 message summary. Related guides: why MIDI sounds different and pitch-bend export limits.