It does work on Firefox and Chromium, although using it on Firefox results in the audio "stuttering" after a while. It also work on my Android's standard webview.
The error I now get in the console while trying to view the site under Epiphany (the site itself shows up completely blank) is
[Error] ReferenceError: Can't find variable: OscillatorNode
(anonymous function) (main.5c6f3cbc.js:1:633013)
t (main.5c6f3cbc.js:1:399164)
(anonymous function) (main.5c6f3cbc.js:1:632972)
(anonymous function) (main.5c6f3cbc.js:1:399088)
(anonymous function) (main.5c6f3cbc.js:1:399096)
(anonymous function) (main.5c6f3cbc.js:1:399122)
e (main.5c6f3cbc.js:1:106)
(anonymous function) (main.5c6f3cbc.js:1:216536)
e (main.5c6f3cbc.js:1:106)
(anonymous function) (main.5c6f3cbc.js:1:110078)
e (main.5c6f3cbc.js:1:106)
(anonymous function) (main.5c6f3cbc.js:1:99264)
e (main.5c6f3cbc.js:1:106)
(anonymous function) (main.5c6f3cbc.js:1:459)
Global Code (main.5c6f3cbc.js:1:469)