No Sound in X

Sound works fine on the normal Trisquel desktop (Gnome when launched automatically by gdm at startup), but if I start X using

xinit

or

startx

, although the window manager or client behaves normally, I can't hear any sound generated by the applications that I run. Strangely enough, I can hear sound from applications running on that X server if I switch to any of the virtual consoles, but when I switch back to X: nothing.

I've tried various ways of starting X or clients with the command

ck-launch-session

, but this hasn't affected any changes.

Does anyone know how to get sound in X when launched from the command line in Trisquel? I'd like to be able to start custom X sessions from the shell.