Mari Kimura is a New York composer and virtuoso violinist whose music includes haunting low notes on the violin called  “subharmonics.”  …Problem is, these sounds aren’t supposed to be possible.
The tones she playes are in the register of a cello, and usually cannot be made from a violin.  Even she is stumped about how it works.  “I don’t really know what it is I do,” she said, because she learned it by “trial and error.”
I don’t know about impossible, but violin subharmonics are certainly gorgeous.