Dance-pop shape-shifters The Chainsmokers are evolving right before our eyes. After a streak of big-tent bangers and Top 40 collaborations (“Roses,” “Closer”), the duo expanded into pop-rock in 2018 with grittier instrumentals, moodier tones, and their own vocals (“Sick Boy,” “Everybody Hates Me”). After drip-feeding those singles into a playlist, they turned that playlist into an official album, Sick Boy, which shows off their songwriting skills, production prowess, and A&R ears. Nashville singer Kelsea Ballerini lifts “This Feeling” into a country-pop crossover, while tracks with producers Aazar (“Siren”) and NGHTMRE (“Save Yourself”) dive straight into the trap/dubstep mosh pit.