I am working on using audio worklets to perform the audio processing without blocking the main UI thread, but support on browsers other than Chrome is still limited.
Should probably put "Works best in chrome" in the project summary for the time being then. I did get it to work in Firefox somewhat with a small sample, but it'd be nice to know this stuff up front before trying. I imagine most people are going to try to load in their one of their full length favourite songs.
Try loading smaller samples or audio snippets.