One hundred years ago An Arc Ascending would have been identified as a 'tone poem,' a work inspired usually by a literary text -- a novel, a poem (as in several Richard Strauss works, for example) -- or, later in the 19th century, a picture (as in Rachmaninov's Isle of the Dead, based on a painting by the popular Swiss-German artist, Arnold Böcklin). In many of these works the composers attempted to follow a specific story line -- take Strauss's Till Eulenspiegel, for example -- almost in the sense of writing a movie script. This turns out to be a somewhat mythical, fictitious process since, unless the composer tells us that his or her piece is based on such and such a text or story, we would never relate the music to that story. (For example, no one would ever be able to guess that Strauss's Till Eulenspiegel is based on the life and ribald pranks of that legendary 14th-century Flemish character, if Strauss hadn't told us so -- even in the very title of the piece.)
Claude Debussy took a slightly different tack than Strauss in his La Mer in that there is not literal story line followed, but instead various general impressions, expressed in musical terms, of visualized (imagined) aspects of the sea. Similarly, Ravel's La Valse is an evocation of an idealized, yet highly personal view of the Viennese waltz genre.
Incidentally, Strauss once bragged that he could even recognizably describe a fork and knife (sic) in music -- which is, of course, utter nonsense. A melody or a given chord or musical idea cannot describe anything concrete; it can at best evoke a mood, an emotion, a feeling, but even then it is likely to evoke quite different moods and feelings with different listeners. That is of course the great beauty and power of music: that it can express everything, precisely because it cannot express or represent anything specific.
My work, An Arc Ascending, falls more into the Debussy/Ravel category, a representation in tones not so much of the actual pictorial content of Alice Weston's remarkable photographs of solstice, equinox, and the historically related ancient native earthworks and mounds, but rather musical reflections on the different seasonal aspects (winter, spring, summer in this case) brought about by the seeming path of the sun in an ascending arc. Actually, since the sun is fixed, it is not ascending at all; it is the earth rotating around the sun at a certain diagonal angle that makes it appear to us earthlings that it (and the moon) rise and fall.
In my piece three of the seasons induced by the sun are represented in several ascending musical arcs, primarily (and in the most immediately audible terms) (1) of rising registers from low (winter) to mid-range (spring) to high (summer); (2) of changing (orchestral) colors from dark murky, wintry grays to spring-like greens to summery yellows and oranges. On another level (or musical track) (3) we can hear the quiet sustained sounds of a cold resting earth -- with occasional low subterranean rumblings; rising in Part Two to the life-giving, undulating, scurrying stirrings of spring -- with brilliant woodwind colors lead to a clash of brightly iridescent harmonies (simultaneously B major, D-flat major, C major), with the former two eventually giving way to the latter, thus leaving a clear climactic C major, portraying the sun at its highest, most glorious, zenith point.