In 1968, along with fellow composers Kurt Schwertsik and Otto Zykan, Gruber was involved in the founding of the 'MOB art and tone ART' ensemble, taking on the role of singer and actor for the first time. Gruber's international career became established when in 1978 Simon Rattle and the Royal Liverpool Philharmonic Orchestra gave the premiere of Frankenstein!! The work has since been performed throughout the musical world - in the orchestral version, the ensemble version, and as a ballet.
Gruber is particularly noted for his concertos, including Aerial for trumpeter Håkan Hardenberger, which has received over 60 performances since its premiere in 1999, two for violinist Ernst Kovacic, the Cello Concertowritten for Yo-Yo Ma and premiered at Tanglewood in 1989, the percussion concerto Rough Music in the repertoire of Evelyn Glennie, and Busking for trumpet, accordion, banjo and string orchestra, premiered by Hardenberger in 2008. Orchestral scores include Dancing in the Dark, premiered by the Vienna Philharmonic Orchestra under Simon Rattle in 2003. Gruber's dramatic works include the apocalyptic operaGomorra staged at the Vienna Volksoper in 1993, Gloria, a musical version of Rudolf Herfurtner's classic pigtale, staged at the 1994 Huddersfield Contemporary Music Festival, Munich Volkstheater, Wien Modern festival, Munster Theater and the Aspen Music Festival, and Der Herr Nordwind to a libretto by HC Artmann, premiered at Zürich Opera in 2005.
As a featured composer, conductor and cabaret artist, Gruber has travelled widely. He regularly performs the chansonnier role in Frankenstein!! internationally and his music theatre repertoire also includes Schoenberg's Pierrot Lunaire, Maxwell Davies's Eight Songs for a Mad King, and works by Kagel. He appeared in performances at the Almeida Festival in 1987, took a leading role in the Alternative Vienna series, presented by the London Philharmonic Orchestra and the South Bank Centre in 1993, and was featured at the Grafenegg Festival in 2011. His close association with the Frankfurt-based Ensemble Modern has included a series of widely acclaimed concerts, opera performances and recordings, and he is increasingly in demand as conductor with the world's leading orchestras, ensembles and music festivals, including his appointment as composer/conductor with the BBC Philharmonic from 2010.
Gruber's recent works include the orchestral suite Northwind Pictures premiered in 2011, a new work for percussion and orchestra entitled into the open..., and an opera based on Horváth's Tales from the Vienna Woods for premiere at the Bregenz Festival in 2014.
HK Gruber is published by Boosey & Hawkes.