Each "Bobby baby, Bobby bubi..." is slightly different that the others. Everyone, I mean each and every person who has done the show, comments on this.
There were 3-4 pit singers, all female in the original, to support the onstage actor-singers in the ensemble numbers like the top of Act Two and the title song with that 45 bar hold. It would be a good idea to include these vocalists who I believed were dubbed "The Vocal Minority".
Bobby needs an actor who sings and has a big range. He also needs staying power since one of the 11:00 songs is his.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher