Kurt Vonnegut drew stories as a single line: up for good fortune, down for ill, from beginning to end. Long pieces of music have shapes too. Pick a work and what the vertical axis measures, and see the story the music tells.
Each work is divided into its named sections: the movements of the symphony, the numbers of the Mass, the scenes of the opera. The time axis is the real running time of one reference recording, taken track by track from MusicBrainz. A section starts exactly where its track starts. Splits within a track are marked ≈ and rounded to the minute, and are only used where the score names the parts.
Each section gets one value per axis, on a deliberately coarse five-step scale. The values are interpretations from the score and the text, not measurements, and half steps would pretend to a precision they do not have. The faint stepped line shows these values as they are. The bold line is a smoothed version, the “shape” in Vonnegut’s sense.
The scales are shared by all three works, so the same number means the same thing in Bach, Mahler and Strauss. Bach’s loudest chorus with trumpets is a 3 for dynamics, because Mahler’s chorus, organ and offstage brass need the 4. Tonal journey is not rated by hand where there is a single key: it is counted from the key signature, as steps around the circle of fifths from the home key, plus one for being anywhere other than home. A relative major or minor is therefore one step away. Strauss modulates so freely that many of his sections have no one key; those are rated by hand and say so.