looks like dmix solves the problem
AFAIK this depends. It solves the problem for apps which want
to access the ALSA device (HW:0 etc.), but as soon as an app
tries to get OSS access via /dev/dsp DMIX cannot do
softwaremixing. Maybe I'm wrong, but AFAIK such apps need to
be started with the aoss wrapper. And no user starts mozilla
as "aoss mozilla", does he?
but it seems like it's
not that easy to set it up (I haven't tried since I have
soundcard with hw support for multiple channels).
AFAIK the latest ALSA and kernel brings DMIX per default
without the need to create an asoundrc.
Best regards
ce