The String Quartet in B minor, Op. 11 was written in 1935–36 by Samuel Barber. Barber arranged the middle movement for string orchestra as his well-known Adagio for Strings in 1936. Barber continued to revise the piece, particularly the finale, until 1943.
Begun while living in Austria with his partner Gian Carlo Menotti after Barber's Prix de Rome, Barber intended that the quartet be premiered by the Curtis String Quartet, but did not finish the piece in time for their concert tour. On September 19, 1936, Barber wrote their cellist Orlando Cole: "I have just finished the slow movement of my quartet today—it is a knockout! Now for a Finale." Having completed a finale, the string quartet was premiered in its provisional form by the Pro Arte Quartet on December 14, 1936, at the Villa Aurelia in Rome. Afterward Barber withdrew the finale so as to rewrite it, which he did by April 1937. He rewrote it again before it was published. The final form was premiered by the Budapest Quartet on May 28, 1943, at the Library of Congress in Washington, D.C.
The opening movement is in sonata form, the second movement a famous adagio, and the final version of the finale, added to the second movement attacca, is shortened, lasting two-minutes, and revisits themes from the opening movement, thereby creating a cyclic form for the quartet. The opening movement has three theme areas, the first a dramatic motif stated in unison by all four instruments, the second slinky chorale like music, and the third a yearning lyrical melody. The quartet as a whole is in the key of B minor, however the central movement is in B♭ minor. The materials of the second movement consist of "a very slow and extended melody built from stepwise intervals, slightly varied in its numerous repetitions, uncoiling over (or in the midst of) sustained chords that change with note-by-note reluctance, all of it building into a powerful climax at the high end of the instruments' range and then quickly receding to the contemplative quietude that ultimately defines this musical expanse."