TEMPO-MAP LIMIT
No. This converter writes one tempo event at the start of its MIDI file, using the BPM selected in the Tempo control. It does not detect changing beats in the source or write a later tempo change. Choose a representative BPM before export. For a performance that speeds up or slows down, import the MIDI into a DAW and build or edit its tempo map there; inspect note positions after each change. The Tempo slider is not an automatic tempo-following switch.
TEST YOUR FILE
The downloaded MIDI uses the selected BPM. This browser tool does not analyze a tempo curve.
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.
SOURCE-CODE CHECK
The current MIDI writer takes the selected BPM, computes microseconds per quarter note as round(60,000,000 / BPM), and writes one FF 51 03 Set Tempo event at tick zero. Its event loop writes note-on and note-off messages; it does not insert another Set Tempo event. The exported file has a fixed tempo until another application edits it.
WHAT THE SLIDER DOES
The writer uses 480 ticks per quarter note. It multiplies detected note times in seconds by the ticks-per-second value derived from your BPM, then optionally rounds those ticks to a quantize grid. Moving Tempo changes the exported beat positions and its single tempo event; it does not listen for a conductor or follow a live drummer.
| Selected BPM | Code formula | Tempo event value | What it means |
|---|---|---|---|
| 120 | round(60,000,000 / 120) | 500,000 microseconds per quarter | One fixed setting written at the start. |
| 90 | round(60,000,000 / 90) | 666,667 microseconds per quarter | Another single fixed setting, not a tempo ramp. |
These values are calculations from this site's current createMidi function, not measured tempo estimates from music. The writer emits a tempo meta-event followed by note events. Download the original calculation sheet to inspect the inputs and formula.
STEADY PERFORMANCE
If the recording follows a known click, select that BPM before conversion. Try Quantize Off first if the performance has expressive timing, then compare the downloaded MIDI against the audio in your DAW. The timing guide separates a tempo mismatch from late playback and missed notes.
RUBATO OR TEMPO CHANGE
Export the detected notes, import the MIDI into a DAW, and place tempo changes at known musical landmarks there. Compare note attacks against the original audio after each edit. If the destination stretches audio when its tempo map changes, check that app's audio-follow settings; this site's MIDI file cannot control them. For grid movement, see the quantization guide.
QUICK ANSWERS
No. It detects note events in audio time but writes one selected BPM at the start of the MIDI file, with no later tempo-map events.
Yes, in a MIDI editor or DAW. Whether audio also follows the tempo change depends on that application's settings, so compare the tracks there.
No. BPM affects exported timing; pitch detection happens separately. Check the source and detection controls for missing notes.
No. Quantize rounds accepted note positions to one selected beat grid. It does not write additional tempo events.