A computer mockup of this pretty lullaby that I wrote for solo viola. The playback doesn’t do many things that a real person would do, like separating strings for triple-stops, but at least this gets the general idea across.
I wrote this using 5-limit just intonation, and those key signatures in the score represent different, specific lattices that can map to something “C-major-ish”. I then draw harmony only from what is “consonantly” available in those lattices, which I think contributed to generating harmonic interest in an otherwise very familiar and simple scale. The hard part was, not being a violist, churning through and making sure that the various multiple-stops are at least physically possible on viola, even if some of them may be pretty odd.
One practical effect that should come out of this is that the violist should not have to make tuning adjustments once a finger is in place. If any violists want to perform this, please let me know!