Glass harmonica

This instrument is played by rubbing a wet finger along the rims of different-sized glass bowls (as one can do with a wineglass), creating different notes. Its sound (another sample here) is pleasant but vaguely unnerving. According to Wikipedia, there is a deep-seated sensory reason for this spookiness:

The somewhat disorienting quality of the ethereal sound is due in part to the way that humans perceive and locate ranges of sounds. Above 4,000 Hertz we primarily use the volume of the sound to differentiate between each ear (left and right) and thus triangulate, or locate, the source. Below 1,000 Hertz we use the 'phase differences' of sound waves arriving at our ears to identify left and right for location. The predominant timbre of the armonica is in the range from 1,000-4,000 hertz, which coincides with the sound range where the brain is 'not quite sure' and thus we have difficulty locating it in space (where it comes from), and referencing the source of the sound (the materials and techniques used to produce it).