"There are many forms of silence," Luigi Nono (1924–1990) once said. "I find silence full of voices." These and other cryptic comments heard in A Trail on the Water (TDK)—an enthralling documentary exploring the unusual friendship shared by pianist Maurizio Pollini, conductor Claudio Abbado, and composer Luigi Nono—illuminate one of the most important composers of the postwar avant-garde.

Unlike his peers such as Boulez, Stockhausen, and Ligeti, Nono remains overlooked due to his overt commitment to leftist politics, the lack of a single English-language book that surveys the immense scope of his work, and a scattered, erratically available discography that keeps fans like me tethered to eBay.

Framed by spectacular shots of the impossibly cerulean sky of Venice, A Trail on the Water teems with reminiscences by Abbado, who championed Nono's orchestral works, Pollini (whose performance of the kinetic ...sofferte onde serene... is an extra on the DVD), Nono's wife Nuria Schoenberg Nono, and others. The documentary is a worthy introduction to a composer whose oeuvre extends from the chilling setting of letters written by condemned anti-fascist guerrillas in Il Canto Sospeso (1955–56) to radical and still-potent electronic music (Remember What They Did to You at Auschwitz) to "scenic actions" (The Forest Is Young and Full of Life, dedicated to the National Front for the Liberation of Vietnam in 1966) to the defiant silences and pealing, reverberant electronics of his late works (Post-Prae-Ludium per Donau) of the 1980s.

Rebellious protest also pervades the music of singer Nina Simone (1933–2003), whose prodigious piano technique embellished Bach-inspired counterpoint with exclamatory flurries up and down the keyboard. A recent spurt of reissues, especially The Soul of Nina Simone (RCA/Legacy), testifies to Simone's defiant, adamantine pride with live-performance footage of "Go to Hell," "Four Women," "Revolution," and other riveting, rabble-rousing songs.