I'm not massively experienced so when i've done auditions (a grand total of 2 ) and the band pull out some originals that i've never heard then it can be kind of daunting, so first run through I just kind of listen and get a feel for the song, locking the timing with the drummer and concentrate on hitting the root notes.
Second run through i listen for where there are holes in what the guitarists are doing... spaces for a wee fill without clanking all over the other parts.
Has worked so far...
And as the Wise Old Git says... you are auditioning them too.
So relax and enjoy it, the worst that can happen is you won't get the place... this will not prevent the sun from rising in the morning and will not cause the earth to spin off its axis.