What mainstream movie (or TV) actors originally got their starts as singers, or for that matter, musicians of any kind. I suppose we could say Roger Daltry, but he’s still not really known as an actor – he hasn’t had that many roles. But I would say that Barbra Streisand qualifies, as I really consider acting to be her real career. I would provisioanlly count Frank Sinatra as well.
Who else?
To prevent this thread from dying a premature death, lets also include stand-up comics turned actors, and movies that were turned into musicals.
Billie Piper (Doctor Who)
Britney Spears (How I Met Your Mother)
Cher (Mask, Moonstruck)
David Bowie (The Prestige)
Harry Connick Jr. (ID4, Copycay, Will & Grace)
Hillary Duff (bunch of Disney crap, War Inc.)
Ice Cube (Friday, Three Kings)
Ice T (New Jack City, Law & Order)
Madonna (Dick Tracy)
Mandy Moore (Saved!)
I’ve excluded singers who only playing themselves, parodies of themselves, or in a handful of films or shows that totally sucked. IOW, no Vanilla Ice Cool as Ice. Britney Spears barely squeeks by for HIMYM whereas Jessica Simpson doesn’t for Dukes of Hazzard
Frank Sinatra won an Oscar, actually. He won Best Supporting Actor for From Here to Eternity. He was in a number of movies that had nothing to do with singing, but also remained a singer.
He didn’t turn into an actor so much as have two careers.
I would discount both Barbra Streisand and Bette Midler on the grounds that they both started out in musical theater and thus were expected to do a certain amount of acting alongside their singing. They didn’t start out as strictly singers, then move on over to acting.
As far as new contributions, I’ll add Sting (Brimstone & Treacle, Quadrophenia, Dune, the Bride).
Well you didn’t say anything about them being good actors…