America's Got Talent revealed its first five Top 20 fourth-season semifinalist acts during Tuesday night's live broadcast of the NBC reality competition series.

Acrodunk, Drew Thomas Magic, Kevin Skinner, and Grandma Lee were revealed to have finished as the top 4 vote-getters after Tuesday night's performance show which featured the season's first group of 12 quarterfinalists performing for home viewer votes, automatically earning them a spot in America's Got Talent fourth-season Top 20 semifinals.

In the process, America's Got Talent host Nick Cannon also revealed that Breaksk8, Lake Houston Dance, Manuela Horn, Mosaic, The Platt Brothers, and the Diva League had received the six lowest home viewer vote totals and been eliminated from the competition.

The announcements then left America's Got Talent judges Piers Morgan, Sharon Osbourne and David Hasselhoff with the task of deciding whether Arcadian Broad or Thia Megia -- the acts that had received the fifth and sixth highest vote totals -- should become the final Group 1 quarterfinalist act to advance to the semifinals.

"Well it's a very difficult choice because you've got two very talented young people but at this stage of the competition I always have the same rule in my head: who has progressed the most in the auditions," Piers said as he revealed his vote.  "Thia, I thought you got much better.  Arcadian, you confused me with the piano playing, I wasn't quite so convinced by your second performance.  My vote goes with Thia."

After noting that both acts had been "fantastic," Sharon cast her vote for Arcadian Broad -- leaving it to David to determine whether Thia, a singer from Tracy, CA, or Arcadian Broad, a dancer from Orlando, FL, would get to advance to the semifinals.

"Thia... this show is about talent and diversity and it's a once in a lifetime gig, but whoever loses can move on and go because you're both incredibly talented," David said as he revealed he was voting for Arcadian Broad.  "You're going to go a long way [but] my choice is Arcadian."

America's Got Talent's next episode will air Tuesday, August 11 and feature 12 more quarterfinalists performing for the chance to advance to the semifinals.