The bassline in Heartbeat is peak 2009 electro. It’s got that gritty, distorted Klaas sound that you just don't hear much anymore in modern house.

"Heartbeat" by is a definitive example of late-2000s electro-house, specifically leaning into the "hands-up" and "fidget" influences that made the German producer a global club staple. Released during the peak of the "Klaas Style"—defined by jagged, saw-tooth basslines and high-energy percussion—the track focuses on a relentless, rhythmic drive rather than complex melodic progression. Sound Design and Production

I remember this playing in every club. It wasn't about the lyrics; it was about that massive pumping side-chain that made the whole room move.