9:14 AM PT -- A set list reportedly showing Sunday's order of performances has been released. It shows Take That as 1st, Robbie Williams 2nd, Niall Horan 3rd, Little Mix 4th, Pharrell 5th, Miley Cyrus 6th, Bieber 7th, Usher 8th, Katy Perry 9th, Coldplay 10th, Black Eyed Peas 11th and then Ariana last.

Ariana Grande's benefit concert in Manchester was moving full steam ahead Sunday ... here she is doing her soundcheck with Miley Cyrus.

Ariana is at the Old Trafford Cricket Ground for Sunday's show, checking her levels and making sure everything is set to go for herself and her supporting cast of performers. She and Miley clearly wanted to warm up their pipes.

Ariana also posed backstage with UK singer Gary Barlow and his band Take That. Seems like they might have been early to arrive seeing how they're local.

Katy Perry, Usher, Justin Bieber, Pharrell and other American acts should be arriving soon if they haven't already.

Meanwhile, hordes of fans are already starting to line up for One Love Manchester. Despite Saturday's terror attack in London ... they mostly seem to be in good spirits.