Most of the Web Audio stuff has already been present in all major browsers for a little while, this mostly standardises what's already there. The main thing that this brings in that up until now was just a feature of Chrome is the AudioWorklet, so real-time low-level audio processing in JS worklets will work cross-browser when its implemented in the other browsers. It's very difficult to implement low-level audio processing off of the main thread in non-Chromium browsers at the moment.