I believe I do have a timeline of events that you might find informative.
Vanessa speaks to the house musicians before a performance by Midnight & Noone.
She tells them that the act do not have tab music and that Miss Midnight (Gally’s stage name) would walk off stage if tab music was played.
They protest and ask to speak to Vanessa’s mother, but Susanna shouts from the wings that they are just to deal with Vanessa.