I'm remembering a few more tidbits:
The actors were asked how their costumes related to the character. Bernadette said that her character wore red so her long-lost love, Ben, wouldn't miss her.
They were asked if they approached the songs differently in the show as compared to singing them in concert. Ron Raines mentioned that people say that they finally understand Sondheim's most well known song "Send in the Clowns" when they see it in
"A Little Night Music." Bernadette stated that she would probably never sing that song in concert unless there were some way to put it in context.