Some might find it astonishing that the string quartets by Beethoven continue to be a defining edifice in the music world.

But once again, there is proof of their endurance: The Cuarteto Casals has chosen to celebrate its 20th anniversary with an international concert tour of the complete set, performed over two weekends in six concerts. Vienna’s turn to hear them starts on February 16.

Perhaps just as astonishing is how young musicians continue to establish fabulous string quartets. Despite being at the cusp of their third decade, the Barcelona-based Cuarteto Casals is a millennial group: some of the members were mere teenagers when it formed in 1997. The quartet already appeared in Vienna in 2006 in the “Rising Stars” series. The star has now risen!

The master composed his sixteen string quartets in three rather distinct blocks; the first six from 1798 to 1800 when he was around 27–30 years old, the next four when he was 35–40, and the last five (plus the Great Fugue) in the final three years of his life. Thus the cliché of defining an artist’s works by the life periods of youth, maturity and old age has also stuck to Beethoven’s quartets: early, middle and late.

The Late Quartets (capitalization intended) are so celebrated that for those “in the know,” one need only mention a number ‒ (opus) 127, 130, 131, 132, 133, 135 ‒ to send shivers down the spine. They contain virtuoso sections that still stretch the abilities of the best, moments of breathtaking beauty, and passages that portend developments a century and more later. Jazz, boogie, clusters, serialism – it’s all hinted at. They are long, complex, unsettling, awe inspiring.

A couple of years ago, Beethoven’s quartets were presented at the Wien Modern festival together with quartets by the 20th-century avant-garde, Schoenberg and Boulez. Hearing these works side-by-side led to an obvious conclusion: Beethoven was 19th-century cutting edge. Igor Stravinsky described the Great Fugue as “an absolutely contemporary piece of music that will be contemporary forever.”

In like fashion, the Cuarteto Casals will perform Beethoven alongside six commissioned works by composers from various Mediterranean countries, including several Y-generationals. I expect the 21st-century state-of-the-art will be an equally fitting companion for him.

Feb. 16, 17, 18, 23, 24, 25 Konzerthaus, 19:30