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"Exercise 15" was made out of and invites transformations or transcriptions. It's for piano or ad hoc instrumental arrangement.
Its material is from a 1920s song "Union Maid" (as I found it in Edith Fowke and Joe Glazer's collection "Songs of Work and Protest") by Woodie Guthrie using an earlier popular song tune. The tempo of the music is not specified.
Sometimes it's played rather fast, as the original tune probably was, sometimes at a deliberate, 'prosaic' tempo.
Here it's in a slow motion as though under a temporal microscope, which to my ears makes it somehow new (extensive change of quantity bringing about a change of quality)". Christian Wolff