There was a sound rarely heard at Glastonbury as Billie Eilish became the youngest person to ever headline the festival: full on high pitched screaming. A hard core of Eilish devotees had packed the front of the Pyramid stage and helped ensure her set was as noisy and exciting as anything in Glastonbury's 50-year history.
At 20, the US superstar certainly wasn't overwhelmed by the occasion, delivering a masterclass in taut, slinky, smart, charismatic modern pop that seemed to go down as well with the regular flag-waving festival veterans as many of her own more (shall we say) highly-wrought fans. The vast crowd of all ages spreading up the hill side were more than welcoming and appeared genuinely entranced by an artist who has the voice, songs, style, personality and sheer joy in performance to put her deservedly amongst pop's greats - for all time, not just this moment in time.
Nevertheless, she is certainly very of this moment. A bone rattling bass synth and barrage of light pyrotechnics announced her entrance, but the opening bombast was sharply undercut by the stripped back, compact, understated tension of opening song Bury a Friend, with a silhouetted Eilish bouncing down a platform, her high energy movements contrasting with her soft, intimate vocals.
This is a big element of her particular dynamic: soft vocals pushed up very high in the mix, underpinned by lean, digitally crafted rhythms and clean, insistent keyboard hooks, and lots of background vocal texture. It's a sound that would be very hard to recreate live without all the wonders of modern technology, which Eilish's production certainly doesn't stint on.
There was a lot of "track", as they say in the live business. Eilish is supported by just two musicians, a pounding drummer giving her often very low-key material more live dynamism and energy, and her multi-instrumentalist co-writing older brother Finneas masterminding everything from behind a keyboard, with occasional forays out to play bass and guitar.
Eilish performs to pre-recorded backing vocals that she adds to live, albeit occasionally letting things roll ahead whilst she runs about smiling, jumping and twisting like the enthusiastic star pupil of a particularly vigorous yoga class. It's hard to bend over backwards and sing at the same time.
During a song called Getting Older (a sensitive ballad about the changes wrought by growing up, reminding us that it is not only the old that worry about aging) some stray vocals appeared in the mix, accompanied by an audible complaint "Get that vocal out of there! Why is it playing?" Albeit, when you have an artist as self-aware and self-referential as Eilish, determined to break down the fourth wall, it is impossible to discount that this might have actually been part of the production.
Sometimes track is used as a form of subterfuge (and can be looked upon suspiciously by more old school analogue musicians and audiences) but a younger generation employ this technology unabashedly, liberated from constraints of band arrangement to create the most compelling spectacle humanly possible. And what the Glastonbury audience got was a hugely slick and entertaining show that was vividly lit, dramatically designed and sounded absolutely fantastic.
Occupying a vast stage as if she was born on it, investing her songs with warmth and passion, and interacting with her audience with twinkling, giggling spontaneity, Eilish offered a very human presence in the pop machine.
During an acoustic interlude, when she played guitar with brother Finneas on their song Your Power, she spoke of her dismay at news from her home country, alluding to the US Supreme Court overturning Roe v Wade's protection of abortion rights. "This song is about power and its use and abuse, and today is a really dark day for women in the US," she said. "I'm just going to say that cos I can't bear to think about it any more in this moment."
For such a generation-defining pop star, it is inspiring to note the care and empathy that informs her clever and emotional songcraft, and underpins her whole performance style. Throughout the show she called on the audience to look after the people around them, and to take moments to take care of themselves. At times, such proclamations risk a certain pious preachiness, especially when addressing an audience that was of a considerably greater age range than her usual fan base. When she encouraged us to all be calm and free and not "give a f--- about anything", a man near me shouted: "What about my gas bill?" to a ripple of laughter.
But still the Glastonbury audience took it all in good part and joined in with Eilish's dance instructions and even participated in a bout of communal screaming in solidarity with her more committed fan base. Only 20 years old and two albums into her career, Eilish commanded Glastonbury with a lot more than mere professionalism, popularity and youthful chutzpah. She has fantastic songs, a gorgeous voice, incredible spirit, and the precious ability to be herself in front of audiences of any size. Paul McCartney, sixty years her senior, is going to have his work cutting out topping that performance.