MIDI Note to Audio Frequency Calculator / Tuning Fork

This utility calculates the audio frequency and MIDI note name from any MIDI note number. Since it is able to play sound, it can also be used as an online tuning fork. It can display frequencies based on any user-defined reference pitch (for A above middle C) between 416 – 466 Hz (default is A = 440 Hz). It also displays the MIDI note name derived from any of the 3 common standards; Middle C = C3, C4 or C5 (default is C4). You can press Play to hear the note at the frequency displayed and you can change the pitch, waveform and volume whether or not sound is playing.

I’ve added a choice of waveforms for playback (because I can! ;)) but do bear in mind that since the default sine wave consists of only the fundamental it is the only pure waveform; all the others contain overtones (or harmonics) of one sort or another:

***Update – 2020-02-12***


  • Note selection is now via a slider (rather than via a number box). Double-click the slider to reset it to the default.
  • A numeric display has been added to the left of the Volume control. Double-click the slider to reset it to the default.
  • Various other minor improvements.


On some Ubuntu/Debian Linux systems it’s possible that the waveform graphics may display incorrectly. Installing the ttf unifont package should fix this issue (from a terminal window, run: sudo apt install ttf-unifont).

On Mac systems, it should now work correctly (I still can’t test it though as I don’t own a Mac). Let me know if you encounter any problems.

MIDI Note to Audio Frequency Calculator / Tuning Fork by Colin Crawley
MIDI note to Audio Frequency
440 Hz
Play Sound


If you find this useful and/or have any comments or suggestions then do let me know via the comment section below.

7 thoughts on “MIDI Note to Audio Frequency Calculator / Tuning Fork”

  1. Thanks for making this tool. I am not a composer or musician, but I have found that I occasionally need to reference frequencies/notes in the course of my work. In the past I have always kept tuner apps on my phone or computer to dial in what I need, but I have stumbled across this twice in the last month and found it very convenient and helpful. Bookmarking for future use!

    Also, it works almost perfectly on a 2014 MacBook Pro running macOS Catalina (10.15.1) in Chrome. The only thing that I’ve noticed is that when you PLAY with the sine waveform selected and then switch to a different waveform with note still playing, sine is still audible along with the new waveform. If you STOP the note, then switch to a different waveform and then PLAY it plays the selected waveform as expected. When you PLAY any waveform other than sine, and then switch to sine, and then switch to something else, it works as expected, playing only the waveform selected. Sine is the only waveform that it does this on.

      1. Hi Shane, I’ve had a look at this now, but I can’t reproduce the issue you’re seeing/hearing at all. Everything seems to work as expected in Chrome and Firefox on both Windows 10 and Linux (well, the non-sine waveforms are a little cleaner on Linux than in Windows, but that’s a different issue). I can’t test Chrome (or any other browser) for macOS specifically as I don’t have a Mac, sorry.

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