Here is Peter Hollens and Sam Tsui's a cappella cover of  Katy Perry's hit song "Dark Horse". The two YouTube stars joined forces to create some harmonic magic in their colorful video.




The duo recorded their vocals "miles and miles apart," Tsui did his part in Los Angeles, while Hollens tackled his side in Eugene, Oregon. Their video arrived one day after Perry released her Cleopatra-themed "Dark Horse" video.