MIDI transposer and tempo changer
Open a .mid file, choose how many semitones to move it and how fast it should play, and download the new file. Every pitched note moves together, the drums stay put, and the key signature is updated to match. The file is changed in this page and never leaves your computer.
Or drop one anywhere in this box.
Transpose a file
- You: Choose a .mid file, type the number of semitones, and press Download the new file. Minus numbers move down.
- The page: Moves every pitched note by that amount, updates the key signature if the file has one, and saves a copy with the change in its name.
- Check: The line under the controls says how many notes move and what the new range is.
Transposing a MIDI file moves the notes themselves, so nothing is lost the way it is when audio is pitch shifted.
Pick the number of semitones
| You want | Semitones |
|---|---|
| One octave up or down | 12 or -12 |
| A whole step up, such as C to D | 2 |
| A song lowered to suit a voice | -1 to -4, then listen |
| A part for trumpet, clarinet or soprano saxophone in B flat | 2 |
| A part for alto saxophone in E flat | 9 |
| A part for horn in F | 7 |
The instrument rows turn a concert pitch file into the part that player reads. Twelve semitones is an octave, and every other shift changes the key. The MIDI note numbers chart shows every note by number and name.
Change the tempo
Tempo is set as a percentage of the original. 100 leaves it alone, 50 is half speed for practicing, and 110 is a tenth faster. The page shows the tempo before and after in beats a minute. Every tempo marking in the file is scaled by the same amount, so a slow ending stays a slow ending. Scaling by a percentage keeps every tempo change inside the song in proportion. A file with no tempo marking plays at 120 BPM, and the page writes one in when you change it.
Know what changes and what does not
- Changed. The note number of every note on, note off and key pressure message on the pitched channels, the key signature, and the tempo markings.
- Not changed. The drums on channel 10, unless you untick the box. Velocities, controllers, program changes, lyrics and the timing of every event.
- Out of range. A note that would go below 0 or above 127 is moved by an octave to stay in range.
Only pitch and speed change, and everything else in the file is left byte for byte as it was.
Hear the result
Open the new file in the MIDI file viewer and player to hear it with a plain tone and to read its new summary, or drag it into GarageBand for real instruments. How to play a MIDI file on a Mac has the steps. Listen before you send the file on, because a key that suits one voice can sit badly for another.
Find the rest of the MIDI tools
This is one of the free MIDI tools on this site, which I run alongside InputConfig, my Mac app for game controllers and MIDI devices. The chord identifier names chords, the BPM to ms calculator turns a tempo into delay times, and MIDI on a Mac links to all of them. Every tool here runs in the browser and keeps your files on your computer.
Questions
How do I transpose a MIDI file?
Open the file here, set the number of semitones to move it up or down, and press Download the new file. Every pitched note moves, and the drums on channel 10 stay where they are.
How do I change the tempo of a MIDI file online?
Open the file here and set Tempo to a percentage: 120 makes it a fifth faster and 50 plays it at half speed. Every tempo marking in the file is scaled, so slow-downs and speed-ups inside the song are kept.
Does transposing a MIDI file lower its quality?
No. A MIDI file holds notes, not sound, so moving the notes changes nothing else. It is not like pitch shifting an audio recording.
Why are the drums not transposed?
On channel 10 each note number is a different drum, so moving the notes would swap the kick for some other drum. The drums are left alone unless you untick the box.
What happens to notes that would go too high or too low?
MIDI notes run from 0 to 127. A note that would leave that range is moved by an octave to stay inside it, and the page tells you how many were.
Is my MIDI file uploaded?
No. The file is read and changed by the page on your own computer, and the new file is made there too.
How many semitones do I transpose for a B flat instrument?
Up 2 semitones for a trumpet, clarinet or soprano saxophone in B flat, so that the written part sounds at concert pitch. An alto saxophone in E flat needs up 9.
Related
Free. macOS 14 or later. No account, nothing leaves your Mac. Open source on GitHub.
Updated