"pas un musée"

Question

why is there no elision between 'pas' and 'un'?

Accepted Answer

Hi Kathleen, 
I think you mean 'liaison' not elision between pas and un.
pas// un OR pas (z)un 
This is one of those 'optional liaisons' and Aurélie decided not to it in this instance,

Optional liaisons =  some liaisons depend on social background, age, mood, and tradition. In this section ‘over liaising’ can sound precious.

e.g.

Pas// aujourd’hui ! OR Pas (z) aujourd'hui ! (Not today!)
Je n’ai pas// appris le français à l’école  OR Je n’ai pas (z) appris le français à l’école ( I didn’t learn French at school)

Hope this helps!