Born in Los Angeles, California, Cline began playing drums with his twin brother, guitarist Nels Cline, at the age of 11. Their first band was called Homogenized Goo and included David Hirschman on guitar. Alex Cline began a musical association with woodwind artist Jamil Shabaka in 1976 as "Duo Infinity". In 1977, he became a member of Vinny Golia's group as well as the Julius Hemphill Trio (along with Baikida Carroll), formed the electric improvisational trio Spiral (with brother Nels and synthesizer player and multi-instrumentalist Brian Horner) and began performing solo percussion concerts.
In 1979, Alex and Nels Cline, along with bassist Eric von Essen and violinist Jeff Gauthier, formed "Quartet Music", a group that enjoyed continued success in its performances and four recordings over an eleven-year period and was awarded grants from the National Endowment for the Arts and the California Arts Council.
In 1982, Alex Cline made his solo debut with Not Alone (Nine Winds), a double LP of percussion music. In 1987, he recorded The Lamp and The Star (ECM), his first album as a bandleader-composer. As the leader of his own group, The Alex Cline Ensemble, he can be heard on Sparks Fly Upward and The Constant Flame, two releases on Cryptogramophone Records, an LA-based independent creative-jazz label. Cline’s other improvisational collaborations include right of violet and The Other Shore, both with Jeff Gauthier and ex-Shadowfax guitarist G.E. Stinson, and Cloud Plate (Cryptogramophone) with Stinson, vocalist Kaoru and koto player Miya Masaoka.
Other groups Cline has led are Alex Cline’s Band of the Moment and The Rain Trio (with Eric Barber and Scott Walton). He has also been involved in duo percussion collaborations with Ron George, Peter Erskine, Christopher Garcia, Andrea Centazzo, Gregg Bendian and Dan Morris, as well as involved in performing the works of composers such as Robert Eriksson, Harold Budd and David Means.
Cline has served as composer and/or performer for numerous modern dancers and dance companies in Los Angeles, including Margaret Schuette, Linda Fowler, the Momentum Company’s "Soundspace" concerts, Dance/LA, the UCLA Dance Company and has enjoyed a longstanding involvement with Will Salmon’s Open Gate Theatre company.
He has participated in performance collaborations with visual artists Yoshio Ikezaki, Norton Wisdom, Kio Griffith and 2-Tu. He has worked on feature and cable television film soundtracks, done numerous sound workshops and percussion clinics, plus lecture-demonstrations on Asian metal percussion instruments. Cline has also been the curator of the Open Gate Theatre’s Sunday Evening Concerts series, a new music/creative jazz showcase held monthly in Eagle Rock, California (since 1997).
Cline has played on over eighty recordings, and has worked with Gregg Bendian, Tim Berne, Arthur Blythe, Bobby Bradford, John Wolf Brennan, John Carter, Buddy Collette, Mark Dresser, Marty Ehrlich, Vinny Golia, Henry Grimes, Charlie Haden, Joseph Jarman, Henry Kaiser, Yusef Lateef, Charles Lloyd, Myra Melford, Frank Morgan, Don Preston, Elliott Sharp, Wadada Leo Smith, Philip Gelb, Richard Grossman, and others.
- Alex Cline/Kaoru/Miya Masaoka/ G.E. Stinson – Cloud Plate (Cryptogramophone CG121)
- Alex Cline Ensemble – The Constant Flame (Cryptogramophone CG110)
- Alex Cline /Jeff Gauthier/G.E. Stinson – The Other Shore (Cryptogramophone CG105)
- Alex Cline – The Lamp and the Star (ECM 1372)
- Alex Cline Ensemble – Sparks Fly Upward (Cryptogramophone CG102)
- Alex Cline /Jeff Gauthier/G.E. Stinson – right of violet (9 Winds 0184)
- Alex Cline Ensemble – Montsalvat (9 Winds 0197)
- Alex Cline – Not Alone (solo percussion music) (9 Winds 0107)
- Nels Cline – New Monastery: A View into the Music of Andrew Hill (Cryptogramophone CG130) (additional percussion, tracks 5 & 7)
- Destroy all Nels Cline (Atavistic ALP122)
- Vinny Golia/Bobby Bradford/Ken Filiano/ Alex Cline – Lineage (9 Winds 0214)
- Gregg Bendian/ Alex Cline – Espiritu (True Media D 98715)
- Stephen Arroyo – The Psychology of the Sun Signs (cassette book w/original music by Alex Cline, CRCS Publications
- Jamil Shabaka/ Alex Cline – Duo Infinity (Aten 0010)
- Layne, Joslyn. "Biography: Alex Cline". Allmusic. Retrieved 13 April 2010.
- "Nels Cline, Alex Cline Interview: An Avant-Jazz Fraternity". NPR. 14 February 2009. Retrieved 27 March 2013.
- DeLuke, R J (9 March 2009). "Alex Cline: Free-Spirited Drummer". All About Jazz. Retrieved 3 September 2011.
- Kelman, John (5 February 2009). "Alex Cline: Continuation (2009)". All About Jazz. Retrieved 3 September 2011.