Thank you. I worked at a TV station like my father before me, and still had no idea.

still lacks kernel audio mixing So does Windows, though. Neither Windows nor Linux uses kernel audio mixing -- they rely on hardware mixing instead. All somewhat modern sound cards have several PCM subchannels that operating systems use in order to play several sounds simultaneously, and, yes, it is perfectly supported by Linux. Last I tried (admittedly, that was some time ago, but I can't remember just how long), using Windows with a single-channel sound card meant that I could only play one sound at a time.

as other posters have said, the Advanced Linux Sound Architecture http://www.alsa-project.org/ has had software mixing for years, but it has only recently become the default behaviour. some window managers (gnome, kde) add a sound-server on top of alsa - there is debate on whether this is a good idea (i don't much like it.)

to emphasize your point, i'd like to add that with the JACK Audio Connection Kit http://jackit.sourceforge.net/ one can get professional quality, low latency mixing and routing between a growing set of ridiculously cool audio/video production tools, so that with (currently) a few custom distributions, and (seemingly soon) out of the box with newer distributions, one can produce a full musical artwork for only the cost of hardware. will the next version of windows include a thousand band equalizer?