ALSA - Multiple Sources...?

[hobie@rumormillnews.com]

For years, ALSA has allowed me to have two apps open at one time - for
example, a YouTube video could be playing in my browser while vlc was also
open, paused on playback of a 3-hour mp3.

That's changed with a recent Debian update.  Now, if a YouTube video is
playing and I try to start vlc, I get an error message:

The audio device "dmix:CARD=CK804,DEV=0" could not be used:
Device or resource busy.

What changed with that recent update?  I have no idea.  After lots of
Internet searching, I put this into an .asoundrc file:

-

pcm.!default {
type plug
slave.pcm "dmixer"
}

pcm.dmixer {
type dmix
ipc_key 1024
slave {
pcm "hw:0,0"
period_time 0
period_size 1024
buffer_size 4096
rate 44100
}
bindings {
0 0
1 1
}
}

ctl.dmixer {
type hw
card 0

-

That made no meaningful change to the situation that I can see.  How can I
bring back the original ALSA behavior that served me so well for years?

Thanks in advance.

--hobie