Taylor Swift dedicated her acoustic guitar mash-up to Max Martin, the Swedish record producer and songwriter, on Sunday (May 19). Taylor Swift's surprise song set transitioned from celebratory to somber in Stockholm. During the acoustic section of her Eras show at Friends Arena, Swift beamed with joy as she dedicated a medley to Sweden’s Max Martin. However, her mood turned melancholic for the live debut of "How Did It End?" from The Tortured Poets Department: The Anthology.