Co-founder of the period ensembles Musica Antiqua Köln and Les Adieux,     Hajo Bäss has toured and given master classes world-wide. He has recorded extensively for EMI, DGG Archiv and New Classical Adventure, garning prestigious international awards and appearing regularly on European radio and television. He is principal viola player with the orchestra Stagione Frankfort, and is also in demand as violinist and viola player with major European orchestras. Hajo Bäss has taught baroque violin at the Scola Cantorum in Basel, Switzerland and given masterclasses in Europe North America and Asia.

Hajo Bäss co-founded Concerto Felice with his former colleague, Musica Antiqua Köln's original harpsichordist Hendrik Bouman. In August 1999, as soloist and concert master he premiered and recorded "live" for CBC/Radio Canada Hendrik Bouman's baroque compositions for orchestra and chamber music and the Fantasy for Violin in G major which Hendrik Bouman composed for him. In Halifax, Canada he premiered Hendrik Bouman's Sonata for Juppes of which he is the dedicatee. In 2002, with Concerto Felice he premiered Hendrik Bouman's baroque music in the Wallonie Festival in Belgium. He also performs Hendrik Bouman's music in his native Germany.

In Autumn 2009 Hajo Bäss joined Hendrik Bouman as principal viola player and soloist of The Baroque Muse in the premiere and recording of Hendrik Bouman's Five Baroque Concertos in Sussex, United Kingdom, released in January 2011. Hendrik Bouman’s wrote his Prelude and Fugue for Viola in F major for him. Hajo Bäss has taught baroque violin at the Scola Cantorum in Basel, Switzerland.