Motorhead's 'Ace of Spades' squares off against Ozzy Osbourne and Randy Rhoads' 'Crazy Train' in a very heavy round three March Riff Madness battle.

Two weeks ago, we started with 32 of rock’s most iconic riffs. Now, that field has been whittled down to eight. We’ll keep going until we theoretically arrive at the most awesome riff in all of rock history.

Motorhead have certainly proven their mettle so far in this tournament, defeating the immortal Black Sabbath in round one and the legendary Deep Purple in round two. Osbourne and Rhoads haven't had an easy path to our "elite eight" either, getting by the Scorpions and then Iron Maiden in their two battles.

So which riff gets to move to the Final Four from the Global Metal region? You can vote once per hour until the quarterfinals of March Riff Madness closes on Sunday, March 23 at 11:59PM ET. The ultimate March Riff Madness winner will be revealed on Tuesday, April 7.

Watch Ozzy and Randy Rhoads Perform 'Crazy Train'

Watch Motorhead Perform 'Ace of Spades'