Livre pour cordes, like so many other works by Pierre Boulez, is a provisional composition, a version of an earlier piece, a "work in progress." Livre pour quatuor was an ambitious string quartet that the young Boulez worked very hard on during the years 1948 - 1949. It was his first composition that didn't include the piano, and he discussed it in some detail in his letters to then-pal, John Cage. Apparently, though, he didn't quite finish it. Four of the projected six movements were completed at that time; a further one was added in 1959, and then the composer abandoned it. One might add that it was fiendishly difficult to play. In returning to the score in 1968, the now seasoned conductor/composer applied his practical knowledge of instruments and performance technique to the task of revising and re-scoring of the quartet for a larger ensemble. An important precedent might be noted in the Lyric Suite of Alban Berg, which was also rescored for string orchestra, and which was a piece Boulez certainly admired. Given his busy conducting schedule, Boulez could only manage to complete the two sections of Movement I: Variation and Mouvement.
Angular and fragmentary, the music owes more to Webern than to Berg. Nonetheless, there is a lyricism running throughout, and the first movement in particular builds up an elaborate contrapuntal texture in which recognizable motifs and lines are played off against one another. Moments of sustained trills or chords, or even of silences, allow the music to breathe. Plucked sounds add a percussive edge to many passages, and other sonorities such as glassy harmonics, tremolos, and sharp accents are used to dramatic effect. At ten minutes in length, Livre pour cordes is a concentrated, engaging work for strings. Boulez returned to it in 1989, revising the score but refrained from adding additional movements. He never returned to the version for string quartet.