Judas Priest's ‘Breaking the Law' takes on Deep Purple’s ‘Smoke on the Water' in round one of Ultimate Classic Rock's March Riff Madness competition.

After much debate, we've selected 32 of classic rock's most iconic riffs and paired them off in 16 first-round duels. Over the next five weeks the field will be repeatedly cut in half by your votes, until we theoretically arrive at the most awesome riff in all of rock history.

This particular Global Metal region battle involves two riff-generating titans. Judas Priest earned their heavy metal stripes throughout the second half of the ‘70s, but it was their first album of the ‘80s that produced perhaps their best-known riff, ‘Breaking the Law,’ which went on to inspire air guitarists around the world.

Deep Purple, for their part, dominated the first half of the ‘70s before devolving into a hard rock soap opera — but not before composing the “mother of all riffs,” learned almost immediately by every wannabe guitar player, the timeless ‘Smoke on the Water.’

So who will win this battle between the '70s first and second halves? You can vote once per hour until round one of our March Riff Madness voting closes on Sunday, March 9 at 11:59PM ET. The ultimate winner will be revealed on April 7.

Watch Judas Priest Perform 'Breaking the Law'

Watch Deep Purple Perform 'Smoke on the Water'