And he was just behind Sinead in our CBBC Newsround Online vote, so he was one of your faves too.
Strap fell off
That means Sinead, David and Lemar are competing in the big final next week.
Sinead and David won the public vote, but then the lucky pair chose Lemar to stay with them.
Sinead wowed the crowds with her version of old classic, One Way Or Another. She even stayed cool when the strap fell off her guitar at the start of the song.
Lemar sang a beautiful version of Nothing Compares 2 U - a hit for Sinead O'Connor in the 90s.
Rock duet
Ainslie impressed everyone when he sang U2's With Or Without You, which even the teachers said was a really hard song. But it wasn't enough to keep him in the Academy on the night.
David went last and sang Freedom, a hit for George Michael and Robbie Williams.
The final four also sang duets as they all sang for survival. Ainslie and Sinead did a lively version of Satisfaction by 60s rockers, The Rolling Stones.
Ronan Keating
Then Lemar and David sang a Stevie Wonder classic, and got the crowds going.
Pop star Ronan Keating then performed a duet with Sinead. They sang one of his own hits, If Tomorrow Never Comes.
The live final will take place on BBC1 next Friday.
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