Ekphrasis is the rendering of a visual work of art into words. I'm not sure what it's called when you render a musical work into words, but I do believe that this little passage by Whitney Balliett about Duke Ellington's "Ko-Ko" is the best example I've ever read.
Take a listen, and read along:
Here is “Ko-Ko,” a minor blues and no relation of Charlie Parker’s “Ko-Ko,” made five years later. It starts in media res. Sonny Greer gives a couple of quick timpani beats, and Carney goes immediately into a chuffing sustained note in his low register—his house-moving register—and is backed by the trombone section, possibly salted with one trumpet. The introduction lasts eight bars. In the first chorus, which is twelve bars, Juan Tizol plays a simple but ingenious six-note figure that is pursued closely by the reed section in such a way that it sounds like a continuation of Tizol’s figure. Tizol stars the sentence and the reeds finish it. In the next two choruses, twelve measures apiece, Tricky Sam Nanton, using a plunger mute, solos against offbeat muted trumpets and the reed section, which plays a sighing three-note figure. Greer punctuates on his tomtoms. In the fourth chorus, also twelve bars, the reeds come to the fore with the same figure they used in the first chorus, and the trumpet section supplies “ooh-wa”s. Ellington himself surfaces from behind, throwing runs and crazy note clusters into the air. The twelve-bar fifth chorus is intense and climactic. The trumpet section plays a repeated long-held note (one of the trumpets, probably Williams, uses a plunger mute) while the saxophone section, broken into two groups, plays accented figures and a melody parallel to the trumpets. The dissonance is almost overpowering. Then the reeds and trombones slide into an eight-bar interlude, pausing for several two-bar breaks by Blanton. In the seventh chorus, the trumpets again play long-held notes, and the saxophones play a countermelody. Carney returns in the final chorus with his very low chuffing note, backed by the trombones. The reeds climb abruptly into view and disappear into a closing full-band chord. The atmosphere of the number is rough and hustling and metallic. There are few treble sounds, and there is little delicacy. The piece bullies us. It sets out to be abrasive and lyrical, and it succeeds. It is also completely an ensemble piece—a kind of concerto for orchestra.
from the New Yorker, January 11, 1982