Colloquially, people use "song", even though "song" has actual specific properties.
What is a generic term for a musical piece? "Musical piece" is OK, but there really should be one that is a single word.
Even "piece" is not very semantic, and it's way too general. If you were to say "piece" without any context, it could be referring to anything: machine parts, body parts, abstract concept parts, etc. It implies other instances of its category. It already assumes a context of a musical composition if it's to be used for the purpose of a generic musical piece. (excuse the circular usage)
A "number" in my opinion is even worse semantically, as it has nothing to do with numerics. And it turns out that it implies that it's part of a collection, which is itself not generic enough http://en.wikipedia.org/wiki/Number_%28music%29 Even worse yet is that the term obscures the collection aspect of its implied meaning, whereas "piece" does not.
(aside: I find the phrase "did a number on you" to be such a semantic monstrosity of an idiom/phrase that it brings up visceral reactions of violence whenever I hear it)
"Composition" is too generic, as it can refer to writing, software, (etc.). It too can implies pieces built up together, albeit internally (e.g. fallacy of composition). Yes, music can be thought of as being made of many musical notes, pauses, (etc.), but that's a superfluous thing to point out, and not as core to the idea of it being music/sound/auditory.
Anyway, a generic term for a musical composition is needed that doesn't necessarily carry implications of it being part of a collection, and actually semantically implies sound/music so that it's not too general.
why has no one coined such a term in English, or if one exists, not used enough to not require such deep thinking to bring it to the forefront of consciousness?