My String Quartet No. 4 was composed in the spring and early summer of 2002, and is dedicated to the memory of Felix Galimir, violinist, master chamber music coach, and long-time inspiring faculty member of the Marlboro summer institute in Vermont. Brian Sands of New Orleans, long-time close friend and admirer of Mr. Galimir commissioned the work on behalf of the Philadelphia Chamber Music Society. The world premiere, by the Juilliard String Quartet, took place on September 21, 2002 in Detroit, Michigan.
The three movements are marked:
I — Lento moderato
II — Allegro energico
III — Lento assai
This quartet represents a departure from my previous three quartets (also all different from each other) in several ways, most notably in its formal plan of two slow movements encompassing a fast one (most three-movement quartets espouse the converse form: one slow movement between two lively tempoed ones). Overall the work's harmonic language is very rich and intense, with lots of eight-part writing. The main body of the first movement features a richly textured, highly chromatic extended episode, in which the three upper instruments (with the first violin in the lead) sing their song over a cello pedal-point lasting — unusual — almost a minute and a half. This episode is recapitulated later in an upside-down version, with the first violin now holding the pedal-point. Another unusual (new for me) feature occurs in the middle of the movement, in which a livelier scatter-shot music alternates abruptly (and audibly) with the slower "pedal-point" music. These dramatic alternations are marked Tempo II and Tempo III.
I was tempted to call the second movement "sound shards" (Klangfetzen in German) or, as Debussy might have done, "storm clouds." This relentlessly driven music eventually subsides into an adagio section, in which two subtly allusive references to Beethoven and Mozart occur. A reprise of the "driven" music closes the second movement.
Tranquility returns in the third movement with a march-like, slow-moving music (in 3/4 time). Here I worked with — again rather unusual — constant alternation of playing with or without vibrato. A delicate, light-textured middle section suddenly explodes into a brief "summer storm" outburst. Four gigantic twelve-note chords herald the final coda of the work, a stately unison passage — with a surprise ending.
— Gunther Schuller