Can a tune with no words be considered a “song?” For example, Bent Fabric’s “Alley Cat,” or Van Halen’s “Eruption” - they are instrumental, but is instrumental just describing the kind of song they are (that is, they are instrumental songs)?
If they can’t be called “songs,” what are they? Tunes?
Yes, technically a song is for the voice. New Harvard defines it as “a form of musical expression in which the human voice has the principal role and is the carrier of a text”.
Some 19th-century composers wrote what they called “Songs without Words” which mimicked the gestalt of a song, but, well, without words.
In general, classical instrumental compositions are called “pieces”.
Fiddlers and bagpipers refer to the “songs” they play as “tunes”.
ETA - missed your question about Bent Fabric and Van Halen - I don’t have a cite, but back in my garage-band days they would be called “instrumentals” as opposed to songs. YMMV depending on age and location.
Of course it depends upon how nitpicky one cares to be, but I think it’s useful to limit “song” to numbers that are sung. For example, I like Irish songs, which have words and are sung. I don’t nearly so much like Irish tunes, typically jigs and reels which in my experience don’t have words. If someone asks my opinion of Irish music, it makes quite a difference whether we’re talking about Irish songs (yay!) or Irish tunes (ho hum).
Musical pieces that never had words can be called tunes, instrumentals, numbers, pieces, and probably a few other terms that aren’t leaping to mind – I don’t see a problem with NOT calling them “songs.” Non-sung versions of songs blur the lines a bit. Perhaps they’re “playing our song,” but no one’s singing – now what? Whether to call it a “song” or a “tune” may depend on the particular situation or other nuances. Then there are pieces that started out as strictly instrumental, but later had words written for them, such as “Sleigh Ride.” So now it is, or can be, a song.
Language use being what it is, a lot of folks will say “song” even if there are no lyrics to sing. I’d prefer they didn’t, but they don’t ask me. 
ETA: You, dear readers, can join the campaign for increased clarity in speech by saving the term “song” for actual songs.
“Eruption” is really a solo, not a song, but instrumentals can be songs (or pass in the vernacular as “songs”) if they follow the basic structure of of conventional vocal song - that is with a repeating melodic motif, especially if it has a verse/chorus structure.
“Eruption” doesn’t really have any of that. It’s just a guitar solo. “Classical Gas” is a “song.”
ETA in my experience playing in bands, I never really heard other musicians arguing that instrumentals weren’t “songs.” or using different words for them.
I disagree. Of course a song must involve singing. I mean, the clue is in the name. The use of “song” to mean any tune, whether accompanied by a vocal or not, is an annoying recent development.
Eh, in my world song just means piece of music. A significant portion of bands I listen to put out both instrumental and vocal music, and it’s way more useful to have a blanket term than it would be to differentiate.
OK, but there are already terms for that, such as “tune”. The word “song” usefully distinguishes between tunes with words and tunes without. Or it did, until people started to ignore the distinction. I mean, why distinguish between tables and chairs? They’re both pieces of furniture.
I suspect it traces back to MP3-organising software that calls everything “songs”. If you’re under a certain age, you don’t get the difference.
Yeah, same here. I know the technical difference, but I haven’t run into anybody (except on the SDMB) who cares. We used “song” to refer to any piece of music we played. Hell, back in my college days I was in an instrumental jam band where everything was an instrumental, and we referred to every piece as a “song.”
Exactly. And what’s with this recent trend of people using the word “hysterical” to refer to emotional excesses, even in men? Of course you can’t have hysteria unless you have a womb. I mean, the clue is in the name.
I detest the practice of referring to all music as “songs,” or all ensembles as “bands.” These terms have specific meaning, and there are other words that better describe these things.
Of course there are the classical composers who wrote “songs without words,” but they knew exactly what they were doing. They didn’t use the term out of ignorance.
I actually lean more in the descriptivist direction than prescriptivist, if that’s what you’re getting at. But that doesn’t mean blindly accepting that every change in language is for the better. In this case I think it is a minor loss, which will no doubt be corrected in due course, either by the adoption of some other term to mean “a tune that is sung” or by a return to the traditional use of “song”.
Birds have ‘songs’, but I’ve yet to hear any words.
All songs are tunes. Not all tunes are songs.
But they are singing. Humans can sing wordlessly too.
I can’t imagine any circumstances in which this happen. Words rarely contract their meanings. That is, once a word has expanded its meaning it will never contract. Older words have narrowed: e.g. meat originally referred to all food before contracting to just flesh.
There still will be technical or professional usages that will continuing making the distinction between music with words and music without. Since that’s a distinction of no value at all for everyday usage, it was dropped. Who is going to change it and why would anyone accept the change?
I agree with the sentiment, but we lost this battle ages ago. In referring to popular music, I hesitate to refer to instrumentals as “tunes” for fear of sounding pedantic.
Song can also refer to a category rather than a piece. “A song by Kenny G” might not have any words, but it can classified as a “song.” Individual pieces that do not have words might not be “songs” by themselves, but can be grouped into the larger category of “songs.”
Another way to think about it is “band.” Yesterday is done by the Beatles, but actually only Paul is singing and playing by himself. Can we actually say it was done by the Beatles?
Also, when classifying music, we can group all of a particular band’s work as “rock and roll,” even though individual songs are in different genres. Yesterday, for example, is clearly a type of ballad or folk song. But, because it was done by the Beatles, it is classified as “Rock and roll.”
But you gave an example of how it happens - you needed to distinguish between the old meaning of “meat” and the new meaning, so you used other terms, such as “all food” and “flesh”. Likewise, if “song” ceases to mean a vocalised tune, some other term, such as the rather clumsy “vocalised tune”, will come into use.
It puzzles me that we can suddenly declare, after hundreds of years, that there is no great need to identify the subcategory of musical works that are performed by means of the voice. Why did we ever have the word “song” in the first place, then?
A tune is technically just a melody, not necessarily a completed piece, with vocals or otherwise. The word does get used in the vernacular interchangably with “song,” though. I think it’s one of those musicians’ jargon things that goes back to jazz musicians, who often thought of the pieces they performed in looser terms - a “tune” was a skeleton they could jam on, not necessarily a precise composition or arrangement.
Sometimes this happens. Often it doesn’t happen. English doesn’t have rules, just usage.
There have been a gazillion threads wondering why there is no terms for the decade ending in 00 or why there isn’t a better term than boyfriend or girlfriend for an adult long-term non-married relationship. Terms, even terms that are obviously needed and useful, may never appear. And there is no obvious need at all for distinguishing between song and tune in everyday speech. But since the distinction is there for technical usage why should yet another term appear?
It might, of course. Terms appear even when there is no obvious need at all.
All words in common use gain, expand, alter, or switch meanings. I think this is one of those times when I can use “all” without the usual weasel words. If a term is used by a living language it will accrue nuances, and eventually those will coalesce into new meanings which will then spawn their own variations. You can decry this with as loud a voice as you want. But you’re doing it yourself every day and all the time without realizing it, and so is everybody else who uses the language.
If there is a need for technical precision, then the language can usually accommodate it. (Although try to define words like liberal or conservative to anyone’s satisfaction.) Neither message boards nor casual speech are normally places for precision. And even when they are, the experts disagree with one another just as loudly.
Close enough isn’t good enough? Sorry. That’s all you can ever hope to get.
The use of “tune” is well-established in some genres and circles and can be upheld more generally by using it. Discussions like this are pedantic, but you don’t need to justify your usage every time you speak. Just say it; the meaning and distinction are readily understood without pedantry.