Before starring as siblings Maddie and Daphne on Nashville, real-life sisters Lennon and Maisy Stella made a name for themselves on YouTube with their folksy covers and adorable sibling chemistry (both on display in their version of Robyn’s “Call Your Girlfriend”). Just in time for Nashville’s winter premiere, the duo uploaded a brand new cover of Charli XCX’s hit single “Boom Clap.” Their slowed-down, harmony-filled take transforms the song from thundering synthpop to haunting ballad.

Although they released an original Christmas tune in December, it’s been almost a year since Lennon and Maisy uploaded a cover to their channel. Thankfully, this one goes a long way to solidifying their position as the coolest 16 and 12-year-old singers on the Internet. [via Vulture]