It's been so long now that a Sweeney Todd revival could actually happen in the next 1-2 years. I still think Bernadette would be a good choice. I think the FOLLIES DC grosses, many of the Broadway gross weeks for FOLLIES, and the fact that she is still performing concerts all over the USA and internationally indicate she is still a name. But unlike FOLLIES, Sweeney Todd is a relatively hot property anyway and can only become more well-known after the release of the Into the Woods film.
Regarding her voice, I just reject that she can't sing the role. It seems like much lesser singers than Bernadette are constantly performing the role on the stage now (e.g., Emma Thompson and Imelda Staunton) but somehow no one seems to care. And she has not missed a single performance of her last several hundred stage performances (i.e., Follies NYC, Follies DC, and A Little Night Music), so she seems to have quite a lot of stamina. Having seen her in concert a couple of months ago, she doesn't sound substantially different from 3 years ago. Bernadette, although aged, is still quite a powerful singer. She is not in the same category of people who can truly not sing very powerfully anymore because of the ageing process (e.g., Lansbury, Rivera, Stritch).
And she has so much she can bring to this role. Very few people can act a song like she can, specifically in terms of her vulnerability. And there is so much vulnerability in Sweeney Todd...."My Friends", "Poor Thing", "Not While I'm Around" - god, the final scene! She also can be incredibly funny (see: NIGHT MUSIC), which will make songs like "A Little Priest" and "No Place Like London" a blast.
Bernadette, please stop trying to sell your house for the 100000th time and play this role

!
Give me claws and a hunch, just away from this bunch.
Updated On: 8/2/14 at 04:42 AM