The only classification system that is close to foolproof is the initial
division of the Library of Congress: Vocal music and Instrumental music.
Under the latter the instrumentation may be specified, with the size of
the ensemble a further refinement--deciding the size limit for "chamber"
is probably arbitrary.  The only extension I might add would be electronic
music as a subclass of instrumental--but that also includes synthesized
voice, so how do you deal with that? Also how much electronic or digital
alteration of originally acoustic sounds does one allow before calling it
"electronic"?

Humans have this penchant for naming and classifying that is recorded as
early as Genesis, I'm afraid.  We like to have our ducks in a row.  It's
useful but should not be confused with finding the truth.

Chris Bonds