J.J. Cale (Dec. 5, 1938 – July 26, 2013): "People have heard my music, but all my famous songs were made famous by somebody else," J.J. Cale once told the Chicago Sun-Times. "But that was my goal." Indeed, a trio of Cale classics—"After Midnight," "Cocaine" and "Call Me the Breeze"—furnished Eric Clapton and Lynyrd Skynyrd, respectively, with three of the biggest hits of their careers. The Oklahoma native released over a dozen albums of his own, helping invent the trademark "Tulsa sound" in the process.

Ray Manzarek (Feb. 12, 1939 – May 20, 2013): Like all great bands, The Doors were blessed with magical musical chemistry. That chemistry could never have existed without Ray Manzarek. The Doors keyboardist's stunning intro for "Light My Fire"--one of the most instantly recognizable song segments in popular music—is but one example of his brilliant artistry. To his credit, Manzarek always insisted each member of The Doors was indispensable in creating their music. "It was transcendent," Manzarek once said, of his years with the band. "Those four personalities fell in line beautifully."

Lou Reed (March 2, 1942 - Oct. 27, 2013): Assessing Lou Reed's impact on rock and roll is a bit like trying to assess Shakespeare's impact on literature. Reed's influence is that fundamental, and it's in the very fabric of the art form. Future historians seeking to assess rock and roll's visceral power--particularly during the second half of the 20th century-could do worse than start with Reed's body of work as a guide. Few artists of any stripe have been as fiercely uncompromising in the pursuit of their craft.

Jeff Hanneman (Jan. 31, 1964 – May 2, 2013): The world of thrash metal suffered a grave loss when guitarist Jeff Hanneman succumbed to liver disease at age 49. As a founding member of Slayer, Hanneman wrote the music (and oftentimes the lyrics) for nearly all the band's best-known songs. The range of artists who cite his influence—both as a guitar player and as a songwriter—is staggering. System of Down bassist Shavo Odadjian went so far as to declare that "without Jeff Hanneman, there would be no System of a Down." Slash simply called him "the king of thrash/speed metal guitar."

Alvin Lee (Dec. 9, 1944 – March 6, 2013): Ten Years After guitarist Alvin Lee exploded onto the world stage following his electrifying performance at Woodstock in 1969. Once called "the fastest guitarist in the West," the British musician was often hailed as an early pioneer in the shredder movement that took hold in the '80s. Lee left Ten Years After in 1975 for a solo career, going on to record with George Harrison, Steve Winwood, Ronnie Wood and other notable figures. In total, he released more than 20 albums during a 45-year career.

Trevor Bolder (June 9, 1950 – May 21, 2013): British musician Trevor Bolder spent most of his 40-year musical career playing bass with Uriah Heep. For fans of '70s glam rock, however, he'll always be best remembered for his work as member of David Bowie's "Ziggy"-era band, The Spiders from Mars. "Clearly the most exciting band Bowie has ever had" is how Rolling Stone once described the Spiders. "Trevor was a wonderful musician and a major inspiration for whichever band he was working with," Bowie said, in the wake of Bolder's death. "But he was foremostly a tremendous guy, a great man."