The show, which opens next week in Cambridge, appears to have potential to be Broadway-bound. WBZ-TVs Liam Martin reports.brGrammy-nominated singer-songwriter Sara Bareilles chats about her new album, “Whats Inside: Songs from Waitress,” which is out today. The songs on the .brThe singer on writing music for the Broadway version of Waitress and the Broadway song she was singing on the top of her lungs at 1:30 a.m..brSara Bareilles sings “She Used to Be Mine” from WAITRESS the new musical based on the film by Adrienne Shelly which premiered at the A.R.T. at Harvard .