Lily Tomlin
Wow - couldn't get over Lily's terrible effort in the singing. I've always been a huge fan - but... She's a veteran stage actor, and CAN sing, however just phones this in. She talks thru the duets with Meryl, not extending words, not syncing, and ending flat with no expression.
I thought maybe this was in her characeter, being washed out and fed up. But if you follow the story, Rhonda is very much an enthusiastic performer, loving to sing and loving this radio show.
So were they afraid to offer vocal arranging and direction to her? When you're performing it can be hard to hear and adjust singing in a live production. I think I'm giving her too much credit - that was just a really bad effort at vocalizing with the clipped, flat lyrics.