Chaplin
Better off silent
One caveat to this one -- this is not an actor that happens to sing in a movie, but the movies they are in must be musicals. This isn't based on one performance, but a body of work, if one exists. Ewan MacGregor can be an answer, even though he was only in one or two musicals (Moulin Rouge) and not a "musical star".
I'm not a musical guy, and there really aren't many male musical stars I appreciate, but I'm going to go with Gene Kelly, who wasn't just a great singer and dancer, but was a very good actor as well.
Honorable Mentions:
Christopher Plummer
Bing Crosby
Fred Astaire
I'm not a musical guy, and there really aren't many male musical stars I appreciate, but I'm going to go with Gene Kelly, who wasn't just a great singer and dancer, but was a very good actor as well.
Honorable Mentions:
Christopher Plummer
Bing Crosby
Fred Astaire