UNTIL DICTIONARIES CHANGE THE MEANING, NOTHING HAS BEEN ALTERED. A song is a song is a song. It's no different than referring to a minuet as an aria. Yes, there is a difference between a symphony and a concerto, although both use the same instruments. Dictionaries are NOT supportive, they DEFINE actual concepts. You do NOT bypass a dictionary to understand a term or word, since the word is explained in the dictionary. Where else are you to look... what logical source of information do you look to, to define a word or concept if not a dictionary? Guitar Player monthly? What grandma told you? And are you aware that the terms in the Oxford Dictionary are based on usage, origins and essential characteristics? Look into that last aspect, and you will realize why an instrument is NOT a song. Some people want their feelings and desires to be supportive, which is subjective and not objective. Seriously, this is basic LOGIC AND REASONING, which some could do with a few classes (and I'm well versed, having written the book Logos, which is Greek for Logic). And Rob, what countries or cultures refer to a song as including instrumentals? Blah, blah, blah. Talk is cheap, but I'm also waiting on those scholarly papers you spoke about. I'm done with this argument, since there is no argument, unless you think defined terms are to be thrown out and YOUR own established as truth. Freaking sad, and people wonder why the West lack intelligence like other countries. They can't even believe their own eyes and ability to comprehend simple terms in a dictionary.
is a songwriter. They both contribute to the finished article of this dictionary definition of a song. 
instrumental songs.
