Post Malone's 21 Savage featured track 'Rockstar' was the most streamed song in the history of Apple Music in its debut week.

It's currently number two on the Billboard Hot 100 to Cardi B's 'Bodak Yellow' and there's a good chance it will be number one next week.

The track's  sinister beat comes from Tank God. If you hadn't heard of him, it's because he's a biology student at the University of Hartford with 750 Twitter followers.

Tank God tells Pigeons and Planes he started working on the beat last December as a way to de-stress during finals. Later, he ran into Post Malone during a trip to NYC and the rest is history.

To me, the melodies are really dark. I was going through a lot of stress," Tank God explained. "It was finals week and I had literally just taken three finals after studying all day. And I was like, “I need to get my mind off this stuff.” So I sat down and made three beats. And that was one of them. Then three days later, I went to New York and played it for Post. Post Malone was in another studio room close by. We ended up crossing paths and I asked him if I could play some beats. He said, "Let's get weird," so I played him that beat and the rest is history," Tank explains. Post recorded a draft of the whole song right there on the spot. You know, like most artists do, he later finalized it and sharpened it and added a feature. So now it's this big record. But he did the rough recording the first day right after I played it for him.

[Related: Crowd fails to catch Post Malone during stage dive.]