In 1906, Tertis stood in for Oskar Nedbal in the famous České Kvarteto. He formed the Chamber Music Players ensemble with William Murdoch (piano), Albert Sammons (violin), and Lauri Kennedy (cello). As a professor of viola at RAM, Lionel Tertis asked many of his colleagues and students to compose for the instrument and greatly expanded its repertoire. Arnold Bax, Frank Bridge, Gustav Holst, Benjamin Dale, York Bowen and Sir William Walton wrote pieces for him. However, Tertis never performed Walton's Viola Concerto as he found it difficult to comprehend at the time; Paul Hindemith gave world premiere of this composition.
Tertis purchased a 17 1/8" Domenico Montagnana 1717 viola in an unplayable condition (without bridge, strings, and fingerboard) during one of the concert tours in Paris. He restored and played the instrument during the twenties and thirties, preferring a large viola for an especially rich tone.