One of the best uses I've found for Csound is experimenting with music in different tuning systems. About a year ago, I got into Pitch Class Sets (even writing a Python module called pcsets). Long before that point, however, I was into jazz, and the traditional chord-scale theory.
All three now collide.
I came up with the idea first: a harp, playing an old exercise I used to play when I was woodshedding -- take a digital pattern, for instance 1231, and play it through a cycle or a chord progression until it was automatic. Except this harp would be played in an alternate universe, where the dominant tuning in jazz was 19-TET, not 12-TET.
As soon as I heard about 19-TET, I liked it. Imagine a world in which C# and Db are separate notes; imagine that there's not just a circle of fourths, but a circle of thirds, a circle of sevenths, and so on. [ Thanks to 19 being a prime number, all of the constant-interval structures eventually map out the entire set . . . as opposed to 12-TET, where there are 4 distinct diminished scales. ]
The chords I've experimented with have taken some getting used to. Being a fretless bass player, I'm pretty sensitive to when something's "out of tune." To be able to compose in 19-TET, I first have to be able to hear in 19-TET.
So my goal was to write an exercise as it would be played by a lightning fast harpist, playing a digital pattern all the way around the circle of fourths. Just for fun, I applied some swing and a little bit of jitter to the note start times. Further, I restricted the pattern to a single octave -- I imagine a 19-string chromatic harp would be a tough instrument to play anyway, not to mention one three octaves wide (57 strings!)
I also took advantage of Csound's "<" operator in the score file to vary the note dynamics (another part of the exercise I used to play).
The exact digital pattern I used was 1235 4321, transposed to start on the 3rd of one chord, and the root of the next.