Our quest to find the best rock album of the ’70s has reached the semi-finals, with just four classic albums left to compete for your votes.

Only Led Zeppelin, Pink Floyd, Tom Petty and the Heartbreakers, and the Who remain. It’s up to you who moves onto the finals.

You can vote once per hour in each of the fourth round brackets, which you will find below. Voting for this round concludes at 11:59 PM EDT on Sunday, March 29. The finals will begin the following morning, and the winner will be crowned on April 1.

The Who's <em>Who's Next</em> vs. Tom Petty's <em>Damn the Torpedoes</em>

The Who’s 1971 album Who’s Next – home to “Baba O’Riley,” “Won’t Get Fooled Again,” and “Behind Blue Eyes” among many others – beat AC/DC’s Highway to Hell by a vote of 57% to 43% to reach the final four. The album had previously dispatched the Beatles’ Let it Be and Van Halen’s 1978 debut album.

After besting Bob Dylan’s Blood on the Tracks and Bob Seger’s Stranger in Town, Tom Petty and the Heartbreakers’ Damn the Torpedoes – which features “Don’t Do Me Like That,” “Refugee,” and “Here Comes My Girl” – beat Rush’s 2112 in a close 51% to 49% race to reach the semifinals.

Pink Floyd’s The Dark Side of the Moon vs. Led Zeppelin’s IV

Pink Floyd’s 1973 masterpiece The Dark Side of the Moon has been the most dominant contender so far in this bracket, dismantling David Bowie’s The Rise and Fall of Ziggy Stardust and the Spiders from Mars, Paul McCartney’s Band on the Run, and the Rolling Stones’ Sticky Fingers, while capturing at least 75% of the vote in all three rounds.

The record will face its toughest competition yet with Led Zeppelin’s 1971 gem IV, home to “Stairway to Heaven,” “Black Dog,” “When the Levee Breaks,” and much more. Zep IV has already stomped all over Elton John’s Goodbye Yellow Brick Road, the Eagles’ Hotel California, and Fleetwood Mac’s Rumours, with 79%, 74%, and 67% of the vote respectively.