The moment of reflection will precede the first act of the day – the Manchester Camerata – playing orchestral versions of dance classics.
Other acts on the bill include The xx, Lorde, Royal Blood and Dizzee Rascal.
Radiohead top the bill, exactly 20 years after their first headline appearance.
Guitarist Ed O’Brien said they would “leave their ego at the gate” and embrace the spirit of the festival.
Footballer David Beckham is also due to visit Worthy Farm on Friday, after organiser Michael Eavis invited him to open a local social housing project.
Although Friday marks the start of festivities, revellers have been arriving since gates opened on Wednesday.
Those in the know were treated to “secret” sets by indie band Circa Waves and alt-pop experimentalists Everything Everything on Thursday night at the small Williams’ Green stage.
For Everything Everything, the short, 40-minute performance gave them the opportunity to revisit the scene of “the best gig we’ve ever had in our lives”.
Two years ago, the band played the stage in the same week they released third album, Get To Heaven, “and in the time that elapsed, the listeners had learnt all the words and were singing them back,” singer John Higgs told BBC News.
“It was a really amazing, moving moment for us all.”
Thursday’s show was almost a re-run of that show, as fans joined in with the band’s new single, Can Do.
Although their set was not part of the official line-up, several thousand fans got wind of the show, and the audience spilled out of the tent into the surrounding fields.
“I keep getting texts from people I haven’t seen for years saying, ‘Oh, you’re playing tonight, aren’t you?'” joked drummer Michael Spearman.
“You can’t really keep anything secret, not in this day and age,” added Higgs.
But, at the time of writing, no-one has guessed the identity of the secret act playing The Park Stage on Friday night.