Now, as Healy sees things, the average seventeen-year-old is worried about melting ice caps, or the failures of capitalism, or how easy it is to say the wrong thing. He sang the song’s refrain: “I’m sorry if you’re living and you’re seventeen.” When Healy and his three bandmates were that age-they have been a band, and best friends, for twenty years-they were mostly concerned with shows, records, parties, and girls, and they believed earnestly in the power of art to free themselves and change the world. Then he lit a cigarette and began to play the jittery riff that opens the band’s latest album, “Being Funny in a Foreign Language.” “You’re making an aesthetic out of not doing well / And mining all the bits of you you think you can sell,” he sang, taking long pulls from a bottle of red wine as the audience roared. His band, the 1975, stood in position among wood-panelled walls and framed family photos, and Healy-skinny, in a close-cut suit and a tie, black curls slicked back behind his ears-rose and dramatically blinked at the lights, took a swig from a flask, and sat down at a piano. In January, the thirty-four-year-old British rock star Matty Healy woke up on a couch in his house, except it was not his house, it was a stage set at the O2 Arena, in London, and twenty thousand people were there with him, screaming.