Born in Zurich in 1952, mathias rüegg completed his studies to become a primary school teacher and taught for a while in various special needs schools. From 1973-1975, he studied classical composition and jazz piano in Graz. In 1976, he moved to Vienna, where he worked as a free-lance pianist. After a while, he got tired of solo work and created the Vienna Art Orchestra in 1977. Since then, he has written almost all of the VAO’s programs,  and has handled the management and organization of the orchestra all by himself. From 1983-87, he also led the Vienna Art Choir. In the years 1984-86, he was voted No.1 Arranger by Down Beat the leading American jazz magazine. He wrote commissioned pieces for other jazz orchestras, such as the NDR Big-Band, SDR Big-Band, Umo Big-Band Helsinki, Swedish Radio Jazz Group and the RTV Big Band Slovenia, as well as for classical orchestras, such as the Wiener Symphoniker, Basler Sinfonietta, Opus Novum, Ensemble Kontrapunkte, Die Reihe, Deutsche Kammerphilharmonie, Orchestre de Normandie Basse and l’Orchestra della Svizzera Italiana. He also led workshops in Vienna, Cologne, Hanover, Berlin, Bern, and Trento. As part of his collaboration with George Tabori and the Serapionstheater, he composed film and theatre music. From 1983 to 1990, he engaged in special projects combining music and literature with the Viennese poet/lyricist Ernst Jandl. Rüegg also worked as artistic director for numerous festivals, including the U & E Third Dream Festival, Jandl Total, Vienna meets Paris, Vienna meets London, and the Alpentöne Festival in Altdorf (CH). In addition, he headed numerous multimedia projects, including Der achte Tag (Wiener Festwochen 1980), Jonny tritt ab (Donaueschin-gen 1981), SENS (Wiener Festwochen 1987), Fe & Males (1989), and La belle at la bête (1992).

For the 1991 Mozart Year, he produced the music film NOT MOZART, on commission by the BBC. Founder of the Viennese jazz and music club Porgy & Bess and also its head until he assigned it to Christoph Huber, he also recently established the Austrian jazz award, the Hans Koller Preis.  Since 1994, he has devoted himself increasingly to chamber music and has written compositions for soloists and chamber orchestra for Corin Curschellas, Michel Portal, Wolfgang Puschnig, Matthieu Michel, and Wolfgang Muthspiel, in addition to a variety of works for other classical ensembles. During 2003, together with Bill Frisell, he was the musical director of the Ruhr Triennale/Festival Century of Song dedicated to the European Song of the 20th century. In 2008, he discontinued the big band and changed the VAO into a chamber group with jazz soloists. The new line-up staged its premiere in May 2009 with the program Third Dream. In the same year, his Piano Concerto No.1 was premiered in the Wiener Konzerthaus. On 9 July 2010, due to financial difficulties, he disbanded the VAO, after their last concert in Viktring/Klagenfurt, at which he presented six of his own arrangements of Mahler lieder.

His new area of activity is the composition of chamber music, which will be published by the Viennese music publishers Doblinger. From 2010 to 2011 he taught at the IPOP (Universität für Musik & darstellende Kunst) in Vienna.

In 2011 he composed the music for the New York based Big Apple Circus and their show Dream Big, which he also rehearsed on-site in the circus as the band leader. Furthermore, he was invited by various big bands to conduct workshops, such as the Conservatory of Vienna (2010), Generations in Frauenfeld, which also led to a reunion of the 80s-line-up of the Vienna Art Orchestra, or the HGM Jazzorckestar Zagreb (2013).