In Latin, the word medulla is often translated as the marrow or soft inner part of an object—not a bad metaphor for the molten core of pure humanism that undergirds Björk’s woozy, elegantly constructed fifth studio album. Released in 2004, Medúlla served as a deliberate pivot from the skittering electronics of 2001’s Vespertine. Björk’s new self-imposed mandate was to build a record almost completely out of a cappella vocals. “I want to see what can be done with the entire emotional range of the human voice—a single voice, a chorus, trained voices, pop voices, folk voices, strange voices,” she told a journalist at the time. “Not just melodies, but everything else—every noise that a throat makes.” The result is a collection of songs that are organic and warmly textured, featuring a panoply of guests, including beatbox legend Rahzel, Robert Wyatt of the prog-rock legends Soft Machine, Inuk throat singer Tanya Tagaq, composer Nico Muhly, and Faith No More vocalist Mike Patton. (Don’t let your ears deceive you: Thanks to Medúlla’s impressive guest list, many of the album’s most “machine”-like moments spring from flesh and bone.) Constructed in sessions across England, Spain, Brazil, New York, and her native Reykjavik, Medúlla is one of Björk’s most political albums—conceived in the wake of 9/11, and its consequent surge of patriotism, jingoism, and generalized fear. Still, hope surges throughout, on tracks like the soulful, swaying opener “Pleasure Is All Mine”; the plaintive “Show Me Forgiveness”; and the propulsive and tuneful “Who Is It (Carry My Joy on the Left, Carry My Pain on the Right).” Medúlla also includes a track heard around the world: The sinuous “Oceania,” which the singer performed in front of an audience of millions at the 2004 Olympics Opening Ceremony in Athens. The song was a fitting summation of one of her most acclaimed works to date: Earthy and alien, tender and surreal—and inimitably, indubitably Björk.