"Definitions of music exist which might exclude singers, solo instrumentalists or percussionists, etc."

Yup, lots of them. Which adhere in vast and populous regions of the world. You might even have someone who lives next door who follows such a definition. And it's equally valid as distinguishing between singing and speaking... though both acts involve the use of voice to make sound that varies in pitch, timbre, and rhythm. Yet somehow one's vocal sounds magically become singing, and this "singing" becomes "music."

It seems to me more understandable (albeit no more "correct") that someone would distinguish between vocal expression in sound and an instrumental expression in sound, and to place the latter in a separate category ("music").