Before they were Maddie and Daphne Conrad in ABC’s country music drama Nashville, real-life sisters Lennon and Maisy Stella dominated YouTube with their massive collective talent by way of unique covers of popular songs. Their cover of Robyn’s “Call Your Girlfriend,” which has gained over 25 million views, is a personal favorite of mine. Though their musical uploads have slowed due to Nashville‘s popularity (the show is currently in its third season), by no means has their collaborative efforts ceased. Need proof? The girls, now aged 15 and 11, perform a stripped down version of Charlie XCX’s “Boom Clap” in the clip above which has already gone viral amassing over 3 million views in under a week. Lennon, the elder Stella, strums an electric sky blue guitar and beautifully harmonizes with her little sister. Together they magically transform a bass-heavy track into a sweet, angelic symphony. Enjoy.