Lennon And Maisy, 'Headlock': Stella Sisters Cover Imogen Heap (VIDEO)

Lennon and Maisy Stella first shot into internet superstardom when their a cappella cover of Robyn's "Call Your Girlfriend" -- performed in the style of Swedish a cappella group Erato -- went viral in June. It even landed the Stella sisters a spot on ABC's new fall show "Nashville," starring Connie Britton and Hayden Panettiere.

Now the internet's most famous preteens have released yet another cover. This time Lennon, 12, and Maisy, 8, took on British songstress Imogen Heap's "Headlock."

Once again, big sister Lennon is the main vocalist, while little sister Maisy provides the harmonies. To put that into perspective: even adult singers struggle with harmonies, so the fact that an 8-year-old has mastered them is pretty impressive. You can also check out Maisy’s rendition of Missy Higgins’s “Secret" if you need an example of this little girl's big voice.

To watch more of Lennon and Maisy's covers, click through the gallery below.