DJ Earworm, also known as Jordan Roseman, pioneered the annual mashup tradition with his 'United States of Pop' series starting in 2008, creating cultural time capsules of each year's biggest songs. The Los Angeles-based artist accidentally discovered mashups while making a road trip mixtape, which went viral and transformed him from an aspiring songwriter into a professional mashup maker who performed at the 2012 Olympics. He observes that music has evolved from the full-on sound of the late 2000s to more introspective styles in the 2010s, and now features sleek, retro-inspired 70s and 80s sounds.