Van Halen's 'Unchained' is lined up against Heart's 'Barracuda' in round one of Ultimate Classic Rock's March Riff Madness competition.

With much difficulty, we 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.

As you can imagine, choosing just one Eddie Van Halen riff from his vast catalog was one of the hardest parts of this process. Ultimately, we went with this hard-charging, flanger-utilizing scorcher from 1981's 'Fair Warning,' which the group frequently uses to open their shows.

They'll be up against some fierce, sharp-toothed competition in the form of Heart's 'Barracuda,' a hard charging riff that kicks off the group's beloved 1977 album 'Little Queen.' (If you were wondering -- yes, a good portion of the office lobbied hard for 'Crazy on You' to represent the Wilson sisters instead.)

So which of these rock legends do you think deserves to move on? 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.

Hear 'Barracuda'

Hear 'Unchained'