Ardour is not connected to jack?

Ja, har for et par dage siden fået Ubuntu studio på min computer, men jeg er løbet ind i et problem med mit program ardour.
Når jeg åbner det kommer der en advarsel frem som siger
Ardour could not connect to JACK
There are several possible reasons:
1) JACK is not running.
2) JACK is running as another user, perhaps root.
3) There is already another client called "ardour".
Please consider the possibilities, and perhaps (re)start JACK


Men hvad er JACK og hvor vil jeg finde det henne?
Tak :P