Love it or hate it, Auto-Tune has changed pop music. From Cher's "Believe" to Kanye West's "Love Lockdown," the sound has penetrated the globe and revolutionized music since its invention in 1997.

How did Sweden become music's stealth superpower? Map its pop trajectory with the arrival of Abba, Ace of Base and producer-songwriter Max Martin.

The Philly Sound meet classic Motown in the impeccable crossover harmonies of Boyz II Men, whose string of smashes inspired a new wave of boy bands.

From Starry outlaws to a "9 to 5" cup of ambition. The lines between country and pop blur with the ascent of Dolly Parton, Willie Nelson and Lil Nas X.

A hit dedicated to another Brill Building songwriter, a strong earworm penned for a cartoon combo - these numbers powered a midcentury music factory.

Can music change the world? Take the pulse of protest music while Hozier, MILCK, Chuck D, the Halluci Nation, Billy Bragg and other weigh in.

From the Human Be-In to Glastonbury, music festivals became a pop rite of passage as onstage electricity connects with an enormous crowd's energy.