Tropos is a single-movement composition for orchestra. The title is Greek for turning, which as a concept is utilized in this piece in two ways. First, the introduction is a rapid presentation of events, each one turning quickly to another in the manner of the images which change as a kaleidoscope is turned. The second aspect of the title's relationship to the piece involves one of the principal motives, which is a slightly expanded turn or cambiata figure. It first appears in the 'cellos in measure nineteen; its harmonized version appears in the horns in measure forty. Each version plays a significant role in the work. The instruments called for in Tropos are four flutes (the second doubling on piccolo), four clarinets (the fourth doubling on bass clarinet), four horns, three trombones, tuba, timpani, triangle, cymbal, glockenspiel, marimba, snare drum, timbales, tom-toms, celesta, and strings. Considerations in choosing this instrumentation were, primarily, the need to set off the 'cellos and the horns as the two important sections and, secondarily, the desire to have an orchestral sound that was somewhat unusual. Tropos utilizes the sonata-allegro principle, with an introduction and coda. The exposition begins in measure eleven. Its first theme, which is lyrical in character, is in two sections. The first opens with the 'cellos' presentation of the theme, which, when joined by the other strings, eventually weaves into a rich interplay of melodies. The cellos emerge from this texture during measures thirty-four through thirty-seven to help to transfer the functional role to the horns. Their thematic presentation begins in measure thirty-eight and is joined by the trombones and tuba in subordinate melodic roles. Accompanying figures during the first theme are taken from the events of the introduction. The second theme, beginning in measure fifty-six, is rhythmic rather than melodic. Its pitches are always clusters -- except in one special case, which is the unison, legato statement of the turn figure by the trombones in measure fifty-nine. The development contains three distinct parts. The first, which is the longest, is generally an evolving variation of the first theme, accompanied by quiet rhythmic quotations of the second theme. During measures 139 through 143» however, these rhythmic accompaniments actually dominate; it is only the violas who remain steadfastly melodic. The second part of the development is at measure 167, the first cue of an unmetered section in which eight solos, joined at 168 by an additional eight, all play quietly, freely, and simultaneously little "music box" melodies. These melodies together represent an ultimate statement of the "intermelodic" aspects of the first-theme section. The third part of the development, beginning at measure 17, is the culminative statement of the rhythmic second theme. Now, devoid of the pitch clusters, and with nonfunctional timpani pitches, the statement of the theme is finally purely rhythmic. The recapitulation is generally subdued, for the statements have all been made and therefore, metaphorically, only the shadows, echoes, and memories remain. In the first-theme section (measures 178 through 21 ) the turn motive never appears melodically. Instead, its only manifestation is in the four horn chords (measures 183, 187, 193, and 198) which are the harmonized version of the motive in extreme augmentation. The second-theme section utilizes rhythmic and cluster elements, with the rhythms now slower and always varied among the instruments. The only melodic movement is the turn motive, itself turned into inverted form. The coda is directly related to the introduction, making use, however, of materials presented during the course of the piece. In addition to the sonata-allegro principle, two other principles are used in the construction of Trottos These are symmetry, regarding principal tonal areas, and the golden section, regarding placement of events in time.