Keith303's "absolutely intersteller"
Keith is one of the worlds best master'er's and just so happened to make one of my favorite songs of all time.
It's mastered to have frequency's flipped between the right and left channels to make it feel like the sound is sweeping around your head.
He goes much farther than your average producer to make his music sound amazing.
On top of that, the song has all the right frequencies to use for testing, wonderful vocals enlaced, a really strong bass presense, and sparkly highs jumping all around your head.
The song was practically MADE for testing headphones.