FREX: a web-based microtonal additive synthesizer


Hi all! I coded this web app over the winter, and a friend told me I should post it here. It’s a keyboard-controlled additive synthesizer which lets you specify its musical scale and harmonic spectrum using a flexible math expression syntax, provided by scalemap.

I hope you enjoy it, and feedback is welcome!



This is so much fun, thank you. Here’s my first experiment with it, channeled through Compass:

The app doesn’t seem to work in Firefox (latest, macOS Catalina), the only thing I could do was start it and play it with the keys in the KEY MAP box. Even though the cursor changes to the text input one when I hover over the other boxes, I can’t actually change anything. Everything seems to work in Safari, though.

Thank you for this!


From a developer position, Firefox is the new Internetexplorer :slight_smile:


Hey, cool sounds! So glad you like it :slight_smile:

At the moment, Firefox doesn’t support contenteditable=plaintext-only elements, which FREX uses for its input text boxes. And being that FF is lagging in its Web Audio support too, I’ve only been testing it in Chrome + Safari so far.

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