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.

Loading Slideshow...
  • "Ho Hey" - The Lumineers

  • "Christmas Coming Home"

  • "Happy Birthday, Harry"

  • 'I Won't Give Up' Jason Mraz cover by Lennon and Maisy Stella

    Lennon 12 and Maisy 8 sing their version of Jason Mraz's I Won't Give Up. These girls are truly amazing. The Stella sisters :) Thank you to Matt Blair for doing this video :)

  • 'When Your Minds Made Up' The Swell Season cover by Lennon Stella 12 & Maisy Stella 7

    12 year old Lennon Stella sings When Your Minds Made Up by The Swell Season. Her sister Maisy Stella 8, sings harmony. It'll make you smile & cry :)

  • Ingrid Michaelson 'You And I' cover by Lennon 10 and Maisy 6

    sisters Lennon 10 and Maisy 6 sing Ingrid Michaelson- you and I cover

  • Live at KX 94.7 -- Lennon and Maisy Stella - When Your Mind's Made Up

    Live at KX 94.7 -- Lennon and Maisy Stella - When Your Mind's Made Up

  • 'Call Your Girlfriend' Robyn/ Erato cover by Lennon & Maisy Stella

    12 and 8 year old sisters Lennon and Maisy sing their version of Robyn/Erato Call Your Girlfriend.

  • Jessie J Price Tag cover by Lennon & Maisy Stella

    Lennon 12 and Maisy 8 sing 'Price Tag' by Jessie J at Pucketts in Leipers Fork, TN

  • Fine Soon - The Stellas (cover by Lennon and Maisy)

    Our children, Lennon (with her grade 4 class) and Maisy (with her SK class), perform a song written by us (the proud parents!) at the school assembly on May 1, 2009. It's even cuter that they're reading buddies.

  • 'Till There Was You' cover by Maisy Stella 7

    Maisy Stella 7 yr old performs Till There Was You @ The Rutledge during Tin Pan South 2011 With Steel Magnolia

  • 'Secret' Missy Higgins cover by Maisy Stella 7

    7yr old Maisy Stella plays and sings Secret by Missy Higgins. Sooo good!

  • John Lennon 'Imagine' cover by Lennon Stella 10

    Lennon Stella 10 years old singing her version of John Lennon's Imagine.

  • Lennon Stella - 11yr old - When It Falls Apart - Matthew Perryman Jones cover

    Lennon Performs 'When It Falls Apart' - by Matthew Perryman Jones @ The Rutledge during TIN PAN SOUTH with Steel Magnolia 2011

Related on HuffPost: