The string quartets of Brahms demonstrate his perfectionism: he wrote dozens of works in the genre, but rejected all but three, and worked at the first one for twenty long years before publishing it. Even the famous Piano Quintet Op. 34 was rewritten several times for various formations before it was published in its final version, whose achievement is today undisputed. These works stepped out of Beethoven's shadow to take a firm place in musical history.

Since its formation in Madrid in 1997, Cuarteto Casals has achieved recognition as one of Europe's most distinguished string quartets.The group came to public attention when it won first prize at both the 2000 London International Competition and the 2002 Brahms International Competition. It now performs regularly in the finest halls in London, Paris, Berlin,Vienna, Zurich,Amsterdam, Madrid, New York and Tokyo, and has appeared at such festivals as Salzburg and Lucerne.The quartet has accompanied the King of Spain on state visits and performed at the Royal Palace of Madrid on the royal family's set of matched Stradivarius instruments. Cuarteto Casals was honoured in 2005 with the Prize of the City of Barcelona, in 2006 with the Spanish National Music Award and in 2008 with the Borletti-Buitoni Trust Award. Claudio Martínez Mehner studied in Madrid, Moscow, Freiburg, Como and Baltimore with Joaquín Soriano, Dmitri Bashkirov,Vitalij Margulis and Leon Fleisher. He has won first prizes in international competitions at Saragossa and Milan and at the Fondation Chimay (Belgium). For many years now he has performed extensively as both soloist and chamber musician in Europe, the USA and Asia.