Born in Zurich in 1974, he studied oboe at that city’s High School of Music (1995–2002). He then studied composition, music theory, and electronic music at the Hanns Eisler Academy of Music in Berlin, graduating in 2007. His teachers included Hanspeter Kyburz, Jörg Mainka, and Wolfgang Heiniger. In 2008/09 he attended the Cursus 1 at the IRCAM in Paris and resided at the Cité des Arts as an awardee of the Berlin Senate. In 2019 he completed a PhD in comparative musicology at the Freie Universität Berlin. In 2006–16 and again since 2020 he has taught at the Hanns Eisler Academy of Music in Berlin. 

Stefan Keller’s numerous artistic accolades include the Kompositionspreis der Landeshauptstadt Stuttgart (2004), two first prizes at the Hanns-Eisler-Preis (2005 and 2006), DAAD scholarships for a stay in Mumbai (2012 and 2013), composition grants from the Senate of Berlin (2015 and 2017), and a Pro Helvetia Residency in India (2018). During his first trip to India in spring 2005, Stefan Keller became acquainted with the North Indian classical music and has since then learnt to play the tabla, an instrument that features in three of his own compositions to date. 

Keller has received many prestigious commissions. His works have entered the repertoires of Ensemble Modern, Ensemble intercontemporain, Ictus Ensemble, KNM Berlin, Zafraan Ensemble, Ensemble Mosaik, Ensemble Ascolta, and Neue Vocalsolisten Stuttgart, among others. 

Selected works: Stück für Orchester (2001–2), Neues Ensemble Stück for flute, oboe, clarinet, quartertone mandolin, guitar, harp, percussion, and string quartet (2003), String Quartet (2004), Camille, chamber opera for two sopranos, actress, and baritone/ countertenor, to a libretto by Reyna Bruns (2006), Sextet for flute, clarinet, piano, violin, viola, and cello (2006), driven for orchestra (2007), Fügung for orchestra (2008–10), Stück für Klavier (2009), Trio for tabla, clarinet, and violin (2008–11), Prélude for tabla and live electronics (2010), Übersteiger for clarinet, bassoon, and percussion (2011), Spring! for instruments and electronics (2011), Kraft in Erscheinung for flute, clarinet, percussion, piano, harp, violin, and cello (2012), Dunkel ist das WAR for soprano, mezzo-soprano, tenor, baritone and bass (2014), Soma oder Die Lust am Fallenlassen for 11 instruments (2015), Hammer for saxophone, percussion and piano (2015), Schaukel for violin, viola and piano (2015), Breathe for piano, electric guitar, accordion and live electronics (2016), Der einsame Tisch for voice and piano to an anagram text by Unica Zürn (2017), Phoenix for tabla and live electronics (2017), hybrid gaits for drumset, keyboard, electric guitar, alto saxophone, trumpet in C and trombone (2017), Persona for bass, tabla, and live electronics (2019–20), Three Songs to Poems by Unica Zürn (2017/20), Nacht for six voices, trombone, and percussion (2021–22), Entangled Strands for tabla and other instruments (2022–23), Elektras Tanz for orchestra (2022), Trance for six instruments (2023), Ein sicherer Hafen for mezzo-soprano, narrator and orchestra (2024).