Every U2 fan knows that the Irish band's sound has changed drastically over the years, from their post-punk beginnings in the late 1970s, to their anthemic rock sound in the 80s and even their brief flirtation with techno music in the 90s. But one thing that has remained consistent is lead singer Bono's emotive voice gracing every single. Except with one major exception, of course.

In 1993, the band gave fans something they weren't expecting by releasing "Numb," a dissonant tune from the experimental album Zooropa (1993). For the track, Bono sat back and let guitarist The Edge - who turns 54 today - sing the tune with a droning voice that perfectly suited the track's title.

The mumbling delivery isn't the only strange thing about the song. According to David Kootnikoff's U2: A Musical Biography (2010), the drumbeat sampled in the track was taken from Leni Riefenstahl's Nazi propaganda film Triumph of the Will (1935). And while taking the album on tour, the band often opened shows with clips from the cinematic love letter to Adolf Hitler.

So there's no doubt that the politically charged group meant something with this crossover. But we'll let you decide what it means. Oh, but we'd be remiss if we didn't point out that the the run time of "Numb" on the album is four minutes and twenty seconds (4:20). Just sayin' is all...

And if you want to hear The Edge sing more, check out U2's Seconds and Van Diemen's Land. Both deep cuts feature the soft-spoken guitarist's vocal work. If nothing else, you can show off your knowledge of U2 lore next time you're having a Guinness with friends. 

And speaking of Bono, click here to see what he and The Boss had to say about Trump during the 2016 election.

Banner image: The Edge, guitarist of the Irish rock band U2, performs live to a packed house in Landover, MD, September 29, 2009. (Ryan Rodrick Beiler / Shutterstock.com)