In the early days of film and television, variety was king. Elvis had starring roles, the Rat Pack all sang in their movies and while Jackie Gleason had one of the highest-rated shows on TV as a bus driver with a comically short fuse, he was also releasing albums of romantic mood music.

But as the modern entertainment industry evolved, the public gradually became less accepting of stars who established themselves in one medium, then tried to succeed in another — especially when these stars established themselves as comedians before trying to cross over as serious musicians (see more on Eddie Murphy and Adam Sandler, below).

But now that reality television is the norm, and participants from those shows seem to be allowed to drift over to any discipline they please (ahem, Heidi Montag), the world might be more accepting of a comic actor who turns to music like Donald Glover. As Troy, the naive and excitable former jock on NBC’s “Community,” he is hilarious, and as a rapper leading Childish Gambino, Glover is more than proficient, rocking a shockingly different persona than viewers may have thought they knew.

» Steve Martin
Martin always put goofy songs on his comedy al-bums and showed early in his career that he was a talented banjo player — though many could have missed this because they were laughing at the arrow through his head. But his 2009 album, “The Crow: New Songs for the 5-String Banjo,” proved he could gracefully transition into a medium that requires players to be well-versed in its tradition. It also helps when Earl Scruggs guests!

» Eddie Murphy
After tucking funny songs between comedy tracks on his albums, Murphy decided to take music seriously. His Rick James-produced anthem, “Party All the Time” went to No. 2 on the charts in 1985. Most of his follow-up singing work was met with less enthusiasm. “Whatzupwitu,” a 1993 duet with Michael Jackson, made listeners wonder the same about Murphy.

»Adam Sandler
Sandler mastered the funny-guy-with-the-guitar thing on “Saturday Night Live,” and some of the songs on his first two comedy albums were absurd enough to make your stomach hurt. But 1997’s “What’s Your Name?” is all songs, and though the musicianship is impressive, the lyrics fly somewhere between funny and sincere and it falls flat.