Swift co-wrote the album with people ''from all different places in music''. Collaborators include Dan Wilson, Butch Walker, Max Martin, Lori McKenna, Ed Sheeran and Mark Foster of Foster The People. Rolling Stone has described the album as ''Swift's most eclectic set ever, ranging from 'State Of Grace', a howling, U2-style epic with reverb-drenched guitars, to a sweet acoustic duet with U.K. singer Ed Sheeran.