Describing the premise of the animated musical comedy “Sing” doesn’t make it sound like a film worth your time and money: A variety of animals compete in a singing competition run by a hustler koala voiced by Texan Matthew McConaughey.

But it’s all about the execution, and writer and director Garth Jennings (“The Hitchhiker’s Guide to the Galaxy,” “Son of Rambow”) has done the impossible and taken that cringe-worthy premise and made a joyous and funny animated feature that will warm your heart.

Seriously. I know.

And this prodigious feat is accomplished by giving this film the tone of the old-school screwball comedies, and McConaughey’s koala Buster Moon is straight out of those black-and-white classics.

Buster has a lifelong love of the theater, so much so that his dad saved all his money to buy him a theater, which he’s run into the ground and is on the verge of losing to the bank. The fast-talking koala’s plan is to hold a singing competition.

Of course, everything goes awry, and Buster struggles to hold everything together. Not to mention there’s a massive collection of singers, each dealing with their own personal issues and motivations for entering the competition.

The singers are an eclectic bunch, from the diminutive Sinatra-inspired mouse Mike (Seth MacFarlane), a soul-singing gorilla Johnny (Taron Egerton), a pig mother named Rosita (Reese Witherspoon), a mother of 25 who is teamed up with flamboyant swine Gunter (Nick Kroll), rocker porcupine Ash (Scarlett Johansson) and shy elephant Meena (Tori Kelly).

Despite thousands of hours of singing competitions having appeared on television (“American Idol,” “The Voice” and more) and in films like the “Pitch Perfect” franchise, “Sing” feels fresh and fun. The choice of music, smartly, is diverse, from pop tunes such as “Call Me Maybe” and “Stay With Me” to classic tunes from The Beatles and Stevie Wonder to crooner standards. There’s certainly something for everyone.

But the music is almost secondary to the conniving Buster and his passion for his theater, and the lengths he’ll go to save it. With his wide eyes and infectious smile, he’s an undeniably lovable character, one of many in a film that inexplicably works.