When Frozen was released at the tail end of 2013, critics praised its sparky lead female characters. But there was a bigger hit lurking within: Let it Go, the Oscar-winning song that has become an LGBT anthem, inspired hundreds of YouTube parody covers and invaded living rooms the world over.

Frozen singalongs in venues including the Royal Albert Hall cemented the song’s success a year after the film’s release. More recently, director Jennifer Lee has apologised to those parents driven to near-insanity by their children’s obsession with Let It Go.

But why is the song so wildly popular? What elements caused Boston Globe columnist Yvonne Abraham to call it “musical crack”? We asked three experts.

1. It's got an irresistible earworm