Dermot Kennedy and David Gray performed with The Cranberries in a surprise appearance on the third day of the Electric Picnic festival at Stradbally, Co Laois.
As the festival winds down, organiser Melvin Benn of Festival Republic said that Kneecap's performance on Saturday night was a "special moment" for Electric Picnic.
He also praised performances by Chappell Roan and Hozier as "insanely good".
Kings Of Leon are headlining this evening's main stage.
"First ever Chappell Roan performance in Ireland and she comes out with a performance like that," he said.
"Hozier, I think, it is seven or eight years since he was here. He has become a global superstar since, an incredible performance.
"I had such pleasure being able to see both of them three times in the last 10 days or so, that was great."
Much attention focused on Kneecap' apperance. The rap trio, made up of Liam O hAnnaidh, Naoise O Caireallain, and JJ O Dochartaigh, are known for their provocative lyrics, championing of the Irish language and their pro-Palestine stance.
O hAnnaidh has appeared in court in London charged with a terrorism offence relating to allegedly displaying a flag in support of Hezbollah during a gig in November 2024. His lawyers have said the case should be thrown out.
Mr Benn said: "I think it was a special moment for the Picnic, I think it was a special moment for them as a band.
"It was easily the largest audience they have ever performed to.
"I don’t think there was anybody anywhere else at the Picnic except watching Kneecap, almost the entire audience seemed to be there, which was a fairly big statement of intent I thought.
"Not just a statement of love of the music but I thought it was a greater statement in that sense. It was great for them."
The promoter said he was surprised that the band paid tribute to him on stage for allowing them to make political statements.
He said: "It is different in the UK, I have had to spend time in their dressing room reading them the riot act about what they can and can’t say in England.
"But those restrictions are not here in Ireland. It was wonderful that they played, I was very pleased that they played."
Mr Benn said there would be some changes ahead of next year’s festival.
He said: "We don’t stand still at the Picnic.
"Headliners, we have got two of the three nights booked, we are in a strong place with that. We are very happy with that.
"I am not going to tell you who they are, so don’t bother asking."
He added: "Not much will change because this is really good."
Mr Benn said the festival would remain at its current size of 80,000 for next year.
Source: Press Association
