I hate app feedback and notification sounds. I hate notifications in general; I prefer to poll for information I need on my schedule. This is also why I hate desktop environments and use a simple full screen window manager. One task at a time. Hell, lately I don't even bring up X every day if I don't need to. Tl;dr: I'm old.
Or wise, and you take control of your own attention.
Multiplexing can be handy if you like gaming, and having music from another application at the same time.
Also sometimes it's useful to have a reference manual in one side of the screen and your text editor in the other, or a PDF viewer on one side and a LaTeX editor in the other.
I'm with you regarding the value of multiplexing. I don't use it much, but it was really annoying back in the day when one program would block another program's sound.
> Also sometimes it's useful to have a reference manual in one side of the screen and your text editor in the other, or a PDF viewer on one side and a LaTeX editor in the other.
True. An emacs which supported the framebuffer could do this (but GNU emacs currently only supports vt100, X, macOS & Windows, IIRC).
There are some framebuffer[1] consoles[2] that work really well when you do need to mux outside of X.
There's nothing quite as jarring as having a pleasant piece of music turned up, only to have some off-key and out-of-time bell ding because an email arrived. Want to let me know there's a new email? Put a little envelope on the task bar so I can see it. Don't invade my music!
Really? So you want all app feedback to cease if you're playing music? No IM or new email notifications? That just seems like a pain to me.