I think that it would be a nice function, when firefox had some sounds (5 or 6 for example) already installed, so that the user can simply change the sound - one example is in the link below.
And sry for my bad english, is not my nature language.
https://www.zedge.net/ringtone/358fe0b2-a6b1-4c71-84a0-59140e6c1107