Audio

Audio in crouton should work out of the box, with sound control synchronized between Chrome OS and crouton. By default, audio is forwarded to Chromium OS Audio Server (CRAS), and you will be able to play audio from both Chromium OS and crouton at the same time, without problem.

If sound doesn't work, upgrading your chroot is very likely to fix your issue.

Pulseaudio

Some applications may not be able to talk with the CRAS plugin directly. In that case, installing pulseaudio may help (most DE/WM start it automatically, but you can also start it manually with pulseaudio --start).

FIXME: Civ V workaround?

Midi

Some applications (dosbox, musescore, a2jmidi, ...) require access to the sequencer (/dev/snd/seq). The simplest fix is to modify /etc/rc.local in the chroot, and add this statement:

chmod a+rw /dev/snd/seq

Then, restart your chroot.

Direct access to the hardware

In some very specific cases (e.g., running advanced audio software where individual outputs is required), you may want to get direct access to the audio hardware. You can do so by adding your chroot user to the hwaudio group.