Princess Charlotte pulled a hilarious baffled facial expression while listening to the opening song of the Coronation concert.
The young royal and other family members are continuing their celebrations after yesterday's Coronation, which saw Charlotte appear as a mini-me version of Kate, wearing an Alexander McQueen dress featuring the same motifs.
The King and Queen are joining around 20,000 members of the public at tonight's concert, which is being hosted by Downton Abbey and Paddington star Hugh Bonneville.
The concert began with DJ Pete Tong playing some Ibiza classics, including 2016 banger Feel The Love, leaving many viewers surprised.
That included Charlotte, who gave an amazing reaction to the song choice as mum Princess Kate looked over.
Before the concert, Tong revealed the the King specifically requested Ibiza classics songs for his concert.
The BBC Radio 1 DJ, who has been tasked with delivering the King's wish, said he hoped it would be a "brilliant" way to start the show.
Speaking to the PA backstage ahead of the event, Tong said: "He wanted Ibiza classics, that was very specific.
"And then they asked us to suggest a couple of songs so we suggested three or four, and he came back with one of them and that’s the one that’s starting the show, so they very much had an involvement in what they wanted us to perform."
Asked why he felt this genre was among the playlist requests, he added: "I think they want to put across a big variety of UK talent and touch all different demographics and be relevant to different age groups.
"I mean, the shows we do we literally get kids up to pensioners. Relapse ravers, we call them – so maybe there’s a few relapsed ravers in the royal household, we don’t know."
The show features performances by Take That, Katy Perry, Lionel Richie, Paloma Faith, Olly Murs, veteran rock guitarist Steve Winwood and Nicole Scherzinger.
Classical acts including Andrea Bocelli, Welsh bass-baritone Sir Bryn Terfel and Chinese pianist Lang Lang are also on the bill.
Hollywood star Tom Cruise, Dynasty actress Dame Joan Collins, adventurer Bear Grylls, singer Sir Tom Jones and former Strictly Come Dancing professional Oti Mabuse are making an appearance via video.
The series of pre-recorded sketches reveal little-known facts about the monarch and include moments from beloved literary character Winnie the Pooh - seemingly echoing the famous moment Paddington Bear drank tea with the Queen during her Platinum Jubilee celebrations.
Nigerian singer Tiwa Savage, DJ Pete Tong with his Ibiza Classics project, and winner of The Piano TV talent show, 13-year-old Lucy, are also performing.
Meanwhile, fashion designer Stella McCartney is delivering a spoken word performance with a conservation theme which will reflect her and the King's "shared passion for environmental sustainability", the BBC has said.
Her performance is part of a broader nature-themed section of the concert which will also include a rendition of a 1980s hit by classical-soul composer Alexis Ffrench and London-based singer-songwriter Zak Abel alongside a house orchestra, band and choir.
Bollywood star Sonam Kapoor is also delivering a spoken-word performance.
The Royal Ballet, the Royal Opera, the Royal Shakespeare Company, the Royal College of Music and the Royal College of Art are coming together for the first time to create a one-off performance featuring Sex Education and Doctor Who star Ncuti Gatwa and Olivier Award nominee Mei Mac.
Former Desert Island Discs and Crimewatch presenter Kirsty Young will anchor the special live broadcast of the concert in the grounds of Windsor Castle after reporting from a studio at Buckingham Palace on Saturday's Coronation day.
The concert on the castle's East Lawn is also seeing TV presenter Clara Amfo and Diversity dance troupe member Jordan Banjo speaking to the artists backstage.
Rendered images released last month revealed that the concert will feature a Union flag-shaped stage which fans out to the audience.
The stage also has a halo-like screen surrounding the roof, which the BBC said will "symbolise the Crown protecting the nation".
Together with the parapet wall steps in the middle, the broadcaster said the staging creates multiple levels for the 74-piece classical ensemble - formed from the strings of the Countess of Wessex's String Orchestra and woodwind, brass and percussion sections from the Bands of the Household Division - to make an abstracted Union flag.
There are four additional catwalks, which also form the flag shape, so fans can see acts close up.
At the back of the stage, the orchestra is sitting in front of the castle.
The Coronation Concert is being broadcast on BBC One, BBC iPlayer, BBC Radio 2 and BBC Sounds today from 8pm.
