example to reflect these two strata. The horn, vibraphone, marimba, and harp represent one stratum of harmonic domain, while clarinet, violin, viola, cello, and piano represent the other harmonic dimension. The vibraphone and marimba parts double the horn, but rhythmically they are usually one 8th-note apart from the horn, which again, similarly to the opening measures, creates a canonic imitation. This mixture of instrumentation is especially effective texturally, since the horn plays longer values, while the other percussion instruments only punctuate these held values with the same notes. The cor anglais and bassoon parts create a completely different canon from the horn. The pitch content for these two instruments is not derived from the trichordal collections (ex. 3.1.2), but are transpositions of the horn part. As mentioned earlier, since the horn part itself is a reordering of the trichordal collections set forth by the viola in the opening, (ex. 3.1.2), the trichords that are articulated by the grace-notes in this horn part will also be different from those collections. For example, in example 3.3.10, the first trichord in the horn part is {A, B, Bb}. The first trichords in both cor anglais and bassoon, likewise articulated by the grace-notes, are {C, C#, D} and {B, C#, C}. These three trichords all belong to the same set-class of (012), and they all represent a different ordering of the (012) trichord. The next trichord in the horn part is {F, C, F#}, while the next trichords in cor anglais and bassoon are {E, Eb, A} and {G#, C#, G}. Again, all three trichords belong to the same setclass of (016), and they all represent a different ordering of the (016) trichord. This process will continue for the following trichords for these instruments (ex. 3.1.10).
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