Professor of composition at Stanford University, he holds a Ph.D from the University of California, San Diego, where he studied primarily with Brian Ferneyhough. His solo, chamber, choral, orchestral, electroacoustic, and operatic works have been performed in both Americas, Europe (including major presentations at the Darmstadt International Summer Courses for New Music), Africa, Australia, and Asia. 

Many of his compositions pose a challenge to the conventional boundaries of musical ontology. These include: works for three conductors and no players, a concerto for florist and orchestra, pieces for instruments made of junk, notational specifications that appear on the faces of custom wristwatches, works for an invented sign language choreographed to sound, amplified Dadaist rituals, and a 72-foot long graphic score displayed in a museum and accompanied by no instructions for its interpretation. His TED Talk—about boredom—has been seen by more than three million viewers. 

Mark Applebaum has been commissioned to write music for Betty Freeman, the Merce Cunningham Dance Company, Fromm Foundation, Kronos Quartet, Wien Modern festival, Paul Dresher Ensemble, St. Lawrence String Quartet, Meridian Arts Ensemble, Chamber Music America, Spoleto Festival, and many others. The San Francisco Contemporary Music Players premiered his composition Rabbit Hole, a chamber ensemble work based on page turns. The composer has engaged in numerous intermedia collaborations, including work with neural artists, filmmakers, performance florists, architects, choreographers, and laptop DJ ensembles. 

Applebaum is also an acclaimed jazz pianist. In this capacity he has concertised from Sumatra to Ouagadougou with his father, composer Bob Applebaum as Applebaum Jazz Piano Duo. They have recorded for Innova, Tzadik, Capstone, Blue Leaf, SEAMUS, New Focus, Champ d’Action, and Evergreen. 

Applebaum serves on the board of Other Minds and as a trustee of Carleton College, where he was also a lecturer. He has also lectured in Antwerp, Santiago, Singapore, Paris, Amsterdam, Copenhagen, Stockholm, and Oxford, and collaborated with the Atlantic Center for the Arts. In 2000 he took up work at Stanford University, where he serves as the founding director of the Stanford Improvisation Collective. He received the 2003 Walter J. Gores Award for excellence in teaching, and was named the Hazy Family University Fellow in Undergraduate Education. 

Selected works (since 2005): 48 Objects for 16 performers (2005), The Blue Cloak for soloist and sextet (2005), Mobile for Paper for any number of performers (2005), Sixteenfor 16 performers (2005), The Bible Without God, improvised piece (2005), Magnetic North for soloist and brass quintet (2006), 48 Objects for 16 performers (2005), Martian Anthropology 4.5.6 – chamber opera (2005), Echolalia, 22 amplified and signal processed Dadaist rituals (2006), 40 Cryptograms 3, improvised piece (2006), Agitprop for symphony orchestra and jazz band (2006), Variations on Variations on a Theme by Mozart for tape (2006), The Composer’s Middle Period for sextet (2007), Sock Monkey for orchestra (2007), Theme in Search of Variations I for trio (2007), On the Nature of the Modern Age for piano duo (2007), Theme in Search of Variations II for quintet (2007), Theme in Search of Variations III for quartet (2007), Medium for quartet (2008), Pause for piano (2009), Straitjacket for percussion quintet (2009), Concerto for Florist and Orchestra (2009), Curb Weight Surgical Field, duo for grand piano and two players (2010), Aphasiafor hand gestures and tape (2010), Coat Room for octet (2012), The Second Decade for percussion quartet (2012), Rabbit Hole for octet (2012), Gone, Dog. Gone! for percussion duo (2012), The First Decade for percussion (2012), 30 for 12 percussionists (2012), The Third Decade for percussion septet (2012), Clicktrack for 12 percussionists (2014), Composition Machine #1 for percussion (2014), Speed Date for violin and cello (2014), Speed Dating for octet (2014), Wristwatch: Speed Dating (2014), Wristwatch: Control Freak for various lineups (2015), Darmstadt Kindergarten for string quartet (2015), Dead Name for string quartet (2017), Administocracy for voice, bass clarinet, trumpet and trombone (2017), Xenophobe: In Memory of Democracy for orchestra (2017), Control Freak for various con figurations of chamber musicians (2015–18).