Though not completed until 1996, the musical materials used in Terry Riley's guitar duet Zamorra originated in an earlier piece—Riley's first composition for guitar, in fact—entitled Ascencion and Zamorra. The complex textures and figurations Riley originally imagined proved impractical for the single performer that Riley had been writing for, however, so he abandoned the project; he later returned to the same musical ideas, recasting them for two guitars instead of one and shortening the title simply to Zamorra (Ascension appeared as the title of yet another guitar work by Riley). Indeed, it is difficult to imagine how one player could have navigated the complex terrain of this short but substantial piece, which, in its duet form, utilizes a wide variety of figurational dialogues, counterpoised melodies, contrapuntal threads, and antiphonal textures.

The piece assumes a strong Spanish character in its minor mode harmonies, chromatic inflections, and aggressive rhythmic articulations. While these characteristics are omnipresent in the work, they continually change in the manner in which they are manifested. There are rarely long stretches of harmonic ambiguity, but Riley nonetheless manages to utilize a broad harmonic palette; likewise, frequent shifts in metrical emphases highlight the contrasts between harmonically lucid, lyrical passages and unexpected chordal excursions, or between the sometimes even percussive dissonances and seamless, virtuosic dovetails of scalar figurations.

Two years after its initial conception, Riley incorporated Zamorra into an extended series of individual pieces and suites, collectively titled The Book of Abbeyozzud. All the pieces in the collection are composed for guitar, either solo or paired with a second guitar or another instrument; in the 1999 recording of the extended work, David Tanenbaum performs Zamorra in tandem with the composer's own son, guitarist Gyan Riley.

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