Hi,
I do use Trisquel for audio production. I only installed a few software from
the official repos (ardour, qjackctl, mixxx, lmms, audacity, zynaddsubfx,...)
and it's sufficient for me. With another french member of trisquel community
we made this small wiki page (in french) about improving trisquel's
performance for audio production.
http://trisquel.info/en/user/login?destination=node%2F14254%23comment-form
Feel free to comment it.
The wiki page contains an all in one command to install a large amount of
audio software from the repos and some indications to handle cpu frequency
(thanks to Dogers). The link to linux-libre-rt is old (looks like it's not
maintained), but you can keep the low-latency core as it is very sufficient
for a daily use.