Meryl Streep's success as an actress is virtually unparalleled; since her emergence in the late '70s, both in theater and film, she has remained a remarkably consistent and versatile performer, respected by her peers and hailed by critics as a once-in-a-generation talent. Though not a professional singer, her roles have occasionally crossed over into music, which she approaches with the same dedication and craft as her acting. Outside of musical theater, she is best known for singing in the popular Mamma Mia! franchise, based on the music of pop group ABBA, as well as the 2014...