When they burst onto the chamber music scene in the 1970s, the Emerson String Quartet were iconoclasts. New York-based, they swapped first and second violin roles, and along with the Brodskys and Kronos they swept away the grand but stuffy tradition embodied by the Amadeus and the Guarneris.

And now, nine Grammys later, they’re continuing to push the boundaries with an intriguing CD featuring the bookends of arguably the most momentous decade ever in classical music.

Joined by long-time collaborators, American violist Paul Neubauer and British cellist Colin Carr, the Emerson’s readings of the great sextets by Tchaikovsky and Schoenberg are like a lesson in musical history. Tchaikovsky, at the beginning of the 1890s, used his Souvenir de Florence (the slow movement was written in the city) to continue the classical traditions that he inherited from his models Mozart and Mendelssohn. Then, at the end of that decade – indeed century – the young Schoenberg in his Transfigured Night sent music into the future, his twisted harmonies depicting haunted forests and psycho-babbling sensualists.

And in this wonderfully-played CD, which is being hailed as a farewell for cellist David Finckel who’s leaving after 34 years, the Emersons and friends do everything to heighten...