All four are fine mature novellas. Though horror fantasy is, by far, not my prefered genre in literature, movies and video games, I enjoyed them all.
The Moon Sliver had very touching moments indeed. It is still The Music Machine that I find the most mesmerizing, for formal reasons, and for the whimsical couple serving as main protagonist.
EDIT: Fingerbones is free, and the three others are now 50% off on Steam, 2 at 1€, and The Music Machine at 2,50€.