For most of the Schubert recordings the instruments were a cello by Francesco Ruggieri (1682), a viola by Carlo Ferdinando Landolfi (18th century), first violin by Domenico Montagnana (1731) and second violin by Carlo Annibale Tononi (18th century).
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By 1975 the group had built up a repertoire of 120 works, including the complete Beethoven, Schubert, Cherubini and Bartók quartets, and works by Haydn, Mozart, Brahms, Hugo Wolf, Pfitzner, Verdi, Donizetti, Debussy, Smetana, Kodály, Janáček, Hindemith, Alban Berg, Gian Francesco Malipiero, Witold Lutosławski, Milko Kelemen, Wittinger and Horvath.
Kronos Quartet | Modern Jazz Quartet | Arditti Quartet | Alban Berg Quartet | Pacifica Quartet | Juilliard String Quartet | Fine Arts Quartet | Emerson String Quartet | quartet | Melos | Amadeus Quartet | Vermeer Quartet | Pro Arte Quartet | Modern Folk Quartet | FLUX Quartet | Belcea Quartet | Ying Quartet | Turtle Island Quartet | Quartet on the Middle East | Petersen Quartet | Ethel (string quartet) | Ciompi Quartet | Smith Quartet | Sacconi Quartet | Quartet | London String Quartet | Homer's Barbershop Quartet | Hollywood String Quartet | Australian String Quartet | Zoellner Quartet |
They have studied with the Alban Berg Quartet, the Artemis Quartet and the Melos Quartet and run masterclasses and collaborations with György Kurtág, Walter Levin, Alfred Brendel, Leon Fleisher and Jörg Widmann.