Spencer Sutherland was the first singer to be voted off and Grace Davies won the first night on Saturday after receiving the most votes from the public.
Here are all the songs and how they were rated by the judges...
Song: What About Us (Pink)
The judges said: Sharon simply described their performance as "phenomenal", saying that they turned the studio into a party and that their performance just "grabbed everybody".
Louis said that the trio "had it all" and that this was "the start of an amazing journey for you" and Nicole was also a fan. Alesha, who was standing in for Simon, said that she knew the absent head judge would be watching at home and be proud of his Group.
Song: Mamacita (Original)
The judges said: "Drop the mic, nailed it!" shouted Sharon. "What can I say? Everything was brilliant - the song, the performance, the staging, the performance. Love it!" Louis thought it was the performance of the night and they had Nicole at "wrap it up like a fajita". Alesha thought the best had been saved until last.
Song: Strong (London Grammar)
The judges said: Sharon loved the song choice, Louis thought it was hard to believe they were so good and so young, but that he didn't "love the song because I think you're so much better than that". Nicole loved Conor's voice and Alesha loved their relationship. "I was lucky to see you at your first audition and what I loved about that was how gritty and raw it was...so please do that again one week"
Song: New Rules (Dua Lipa)
The judges said: "Everytime I see you, you make me smile," said Sharon, who also said she was "so glad" they were back in the competition. Louis didn't think the boys realised how good they were - despite the fact he called them "Jack and Jo-elle". You can't have it all, eh?
"You both complement each over so much," said Nicole, pointing out Jack's vocals in particular for praise. Alesha thought the pair were very well-spoken and branded them "posh rappers" - but we think it was a compliment!
Song: What Makes You Beautiful (One Direction)
The judges said: Louis said that Talia reminded him of a young Barbara Streisand (of course she does Louis), while Sharon said that she "didn't recognise" the new-look Talia. Although bringing the spirit and the embodiment of Simon Cowell, Alesha Dixon said she didn't love the arrangement of the One Direction song and that she should do something a bit more up-tempo next week.
Song: Stay (Rihanna ft Mikky Ekko)
The judges said: "Everything about that was perfect," said Louis, who reckoned that Kevin was "in a different league" to the other acts in the competition and ended it with a "merci beaucoup". Sharon reckoned that his rendition of 'Stay' suited his voice, while Alesha Dixon thought that it didn't get much better than that in terms of performing.
His judge Nicole Scherzinger loved it so much she started straddling the desk!
Song: Scars to Your Beautiful (Alessia Cara)
The judges said: "No way are you going back to your day job after that," said Louis, who also reckoned that Matt had a great likability. Sharon reckoned that Matt was "trouble with a capital T", although didn't really have any evidence to back it up with. She also thought that it was the performance of the night so far, with Alesha thinking there was more for him to give. Nicole said she was "so proud" of Matt and that we "all wanted to roll up to Matt's voice like an egg roll".
Nope, us neither.
Song: Written in the Water (Gin Wigmore)
The judges said: She got a standing ovation from all four of the judges after her performance, with Louis Walsh saying that he could hear some Amy Winehouse in her voice. "I loved you from the first time I met you," said Sharon, who added that "yes, you do sound like Amy Winehouse!" Alesha had been really looking forward to hearing Traceyleanne and she wasn't disappointed. Her mentor Nicole, meanwhile, was "lost for words".