Born in 1956 in Dublin, he grew up in Scotland in a family in  which every member played a different musical instrument. As  the youngest of four children who all played string instruments,  he chose the viola. After studying at the Royal College of Music in  London under Frederick Riddle, he became a member of Pierre  Boulez’s Ensemble intercontemporain in Paris (1983–90) and subsequently joined the Arditti Quartet in London (1990–97). He has  given numerous premieres and cooperated with most of the leading contemporary composers, including György Ligeti, Iannis  Xenakis, Karlheinz Stockhausen, Pierre Boulez, György Kurtág,  Salvatore Sciarrino, and Hans Werner Henze. He currently performs as a soloist on viola and viola d’amore. He lives in Paris.

He has made numerous recordings as a member of the Arditti  Quartet and the Ensemble intercontemporain. His first solo  album, Works for Viola, released by Naïve Records, was honoured  with the Deutscher Schallplattenpreis. His next album, Spectral  Viola, was released by Zeitklang, while his album devoted to  the viola d’amore, released by ECM Records, was named Album  of the Month by the British magazine Gramophone (September  2008). In 2009 Garth Knox recorded another album for ECM,  released in 2012 under the title Saltarello. Knox (medieval vielle, viola and viola d’amore) is joined by Agnes Vesterman (cello) and  Sylvain Lemêtre (percussion). The album’s repertoire spans compositions from the medieval period (Hildegard von Bingen, Guillaume de Machaut), through the Renaissance (John Dowland)  and Baroque (Henry Purcell, Antonio Vivaldi), to contemporary  music, represented by Kaija Saariaho and Garth Knox himself.  The album has also been praised by jazz critics.

In recent years, thanks to his interest in the viola d’amore and  the medieval vielle, his repertoire has expanded to include early  music—medieval and Baroque—which he convincingly brings  into a contemporary performance context. His Irish-Scottish  roots, meanwhile, allow him to carry on a free dialogue with traditional Celtic music. He has always felt himself to be an improviser as well, and increasingly also a composer, developing his  own musical ideas in the form of an innovative instrumental  theatre.

Selected works: Fuga Libre for viola (1990), Malor me bat for  viola d’amore and cello (2004), La Valse de la Vineuse for viola  d’amore, clarinet, violin and cello (2006), Ockeghem Fantasy for  viola d’amore and five violas (2008), Viola Spaces, eight concert  etudes for viola (2004–9), Wild Animals for viola, flute, clarinet,  violin and cello (2011), The Weaver’s Grave for string quintet  (2011), Three Weddings and a Fight for viola (2013), Stranger for  viola and viola d’amore (2013), Nothing but the Truth for string  sextet (2014), Satellites for string quartet (2015), Air and Ground  for viola d’amore and five instruments (2016), Violin Spaces, nine  concert etudes for violin (2018), Three New Spaces for Viola (2023).