After fixing a billion of other things on my M9 upgraded to hardy, my daughter wanted me to double click on the musical notes icon of an mp3 I had on my desktop. And lo and behold: Audio did not work. Didn’t find anything M9 specific. Having read about people complaining about the switch to pulseaudio in hardy, that was my first suspicion, and the M9 doesn’t seem to be too common. It didn’t prove to be the culprit. It was the Intel HDA chip and alsa, rather. Turns out alsa nowadays needs to be told what specific chipset you want for selecting a codec.
This lead the way:
That page is in German, but the most valuable hint is to verify you have the HDA sound card by looking at /proc/asound/cards. Then find a suitable codec by doing:
head -n 1 /proc/asound/card0/codec*
Finally read /usr/share/doc/alsa-base/driver/ALSA-Configuration.txt.gz and select a suitable option to append to /etc/modprobe.d/alsa-base. For the M9 that is:
options snd-hda-intel model=fujitsu