Strobe lights and garish get-ups gave way to side partings and swing as the X Factor ditched last week's disco theme in favour of the big band sound for tonight's live episode.
Backed by a 30-piece band, it was Rough Copy who stole the show with a contemporary twist on a classic Ray Charles number, as some of the acts appeared to struggle to win over the judges.
Opening the programme, the normally bespectacled Abi Alton split the panel with her rendition of Frank Sinatra's T hat's Life, which she dedicated to her father.
Louis Walsh said: "It didn't go too far for me. I think you can do so much better."
But Nicole Scherzinger replied: "She was sass-tastic tonight. You let go, you had so much fun with it, girl. You delivered tonight."
Sam Bailey, the sole representative in the Over-25s category, also borrowed from Old Blue Eyes' back catalogue, taking on New York, New York.
Gary Barlow described her performance as "unbelievable", while Walsh went further in his praise, saying: "For me, you are the one to beat in the competition."
Sixteen-year-old Nicholas Mc Donald's version of Ella FItzgerald's Dream A Little Dream Of Me earned him the moniker "Baby Buble" in reference to the Canadian crooner Michael Buble.
Sharon Osborne said: "You embraced big band week fantastically. You totally put yourself into it."
Devon teenager Luke Friend, with his trademark unkempt hair scraped back into slick ponytail, sang Moondance by Van Morrison. But he did not enjoy a vintage evening. Barlow told him: "I was disappointed in that tonight. This style just doesn't suit you at all."
Both he and former Pussycat Dolls singer Scherzinger said Friend needed to sing "behind the beat", rather than ahead of it.
But the mood lifted when Hannah Barrett performed the James Brown classic It's A Man's Man's World. Osborne told her: "We had more of that lovely hot chocolate voice of yours. We can never get enough of you."
Walsh added: "You're doing something right."
There was a change of pace as Rough Copy - the only group left in the competition - added a contemporary twist to Ray Charles's up-tempo Hit The Road Jack.
The trio, performing with canes and crimson blazers, swaggered around the stage as they produced an energetic rendition replete with leather trousers and tight choreography.
Both Scherzinger and Walsh tipped the trio to make the final, with the latter adding: "You are slick, snazzy - I love the style. You have to make the final."
Tamera Foster, who was seen weeping after being in the bottom two last week, impressed tonight when she took on Julie London's Cry Me A River - even if Osborne once again stumbled over pronouncing the 16-year-old's name.
Barlow said her potential was "stratospheric", while Walsh described her as a "little diva", and said: "You've got this thing called 'star quality'."
Sam Callahan brought the curtain down on the show, with a cover of Dean Martin's Ain't That A Kick In The Head.
The judges gave him "A for effort", while Walsh, dipping into the show's bag of catchphrases, added: "You're like a little Fred Astaire."
The acts will return tomorrow night when they learn who will go through to the next round.