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:

**Notes**

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.

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).