Stefan Keller studied the oboe, then composition at Zurich University of the Arts. After obtaining a performance degree in oboe, he studied at Utrechts Conservatorium, then at the Hochschule für Musik Hanns Eisler Berlin, where he took composition with Hanspeter Kyburz, music theory with Jörg Mainka, and electronic music with Wolfgang Heiniger.

In 2008-2009, he attended the Cursus I program in composition at IRCAM in Paris, where he was also a resident at the Cité des Arts through a Berlin Senate scholarship. In 2011, he received help from the Center for Contemporary Arts, Berlin.

From his first trip to India in 2005, Keller became interested in North Indian classical music and began studying the tabla with Gert-Matthias Wegner. He composed Trio for tabla, clarinet, and French horn in 2008, producing another version for tabla, clarinet, and violin in 2011, and Prélude for tabla and live electronics, which he debuted himself in 2010. He continued this exploration with Phoenix (2017) for tabla and live electronics and Persona (2020) for voice, tabla, and live electronics.

One of his chamber music pieces, Übersteiger, was commissioned by the Ensemble intercontemporain and debuted in 2011. He also composed a chamber opera, Camille (2006), and a piece for orchestra, Fügung, as part of the Elsa-Neumann-Stipendium (NaFöG) awarded by the city of Berlin. In 2014 and 2017, he was awarded a composition grant from the Berlin Senate.

Keller has been awarded several prizes from the Swiss composers’ association. He also won first prize in the 2002 SJSO Competition, the Composition Prize of the City of Stuttgart in 2004, the Hanns Eisler First Prizes in 2005 and 2006, and the Hochschule für Musik in Berlin Startup Prize.

From 2006 to 2016, he taught writing, harmony, counterpoint, and analysis at the Hochschule für Musik Hanns Eisler in Berlin. In 2016, he was head of Klangzeitort, the institute for contemporary music in Berlin. From 2014 to 2019, he wrote a thesis in comparative musicology at Freie Universität Berlin. Between 2017 to 2020, he was artist-in-residence at Villa Schoeck in Brunnen, Switzerland, then in Mumbai, then at the Villa Serpentara in Olevano, Italy, and finally at Villa Massimo in Rome.