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 390 – 490 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.

It’s also useful for cases where you might need to calculate an exact frequency for “surgical” EQ-ing.

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:


On some Ubuntu/Debian Linux systems it’s possible that the waveform graphics may display incorrectly. Installing the ttf unifont package should fix this problem (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 difficulties.

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 (please read our website rules before posting).

***New Plugin Now Available!***

For anyone who, like me, uses REAPER  (Digital Audio Workstation software), I have now made this utility available free of charge as a native REAPER JSFX plugin. Do feel free to download it and send me some (constructive) feedback:

Update – 2020-04-17:

By popular request, the Concert A reference frequency range has been extended and is now variable between 390 – 490 Hz (default is 440 Hz) in both the online calculator and the JSFX plugin. If you downloaded the plugin before 17th April 2020, you may want to download the updated version (click the button below).

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

  1. Colin, thank you for providing this useful app with precision frequencies. As a 5-string banjo player, I am used to hearing other musicians claiming “a banjo is never in tune” and I have vowed to make my 1912 Tubaphone as “in tune” as I can make it. Bart Veerman in Hamilton, Ontario makes compensated banjo bridges, but requires accurate measurements of out-of-tune-ness for each of four strings. Can your FC/TF display the fundamental frequency of a note played on a stringed instrument? That would be “the schnitzel” for my need. I can get a decent microphone plugged into my USB port.
    Thanks again for making this fascinating app.

    1. Hello Rich,

      Thanks for your message. I’m very glad to hear you’re finding this utility useful.

      In answer to your question, the tone generator aspect of this utility is designed to function in a similar way to – but with much more flexibility than – a traditional, physical tuning fork (i.e. to provide a reference tone). It does not function as a “tuner” (i.e. able to “listen” to and analyse audio input). Luthiers generally use a strobe tuner for the sort of thing you describe anyway (i.e. instrument setups) because of the high precision they afford but for day-to-day use there are also plenty of tuners already available both in hardware and software (many inexpensive or even free). For that reason I would rather invest my time a bit more creatively rather than trying to reinvent that particular “wheel” here.

        1. You’re most welcome, Rich. It’s good to know that if I’m allowed to ramble on for long enough, something useful can eventually come out! 😉

          Good luck with your “Tubaphone” setup.

          By the way, there’s an informative video about how strobe tuners work here.

  2. 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.

        1. No worries, still totally useable. I was just reporting the trivial bug that I was experiencing since you commented on testing on mac in your post.

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