Catching up on New Yorkers, I happened on a poem by John Koethe, which begins:
It’s a great poem, but, needless to say, what mainly interested me was Koethe’s use of covers band instead of cover band — to mean a musical combo whose repertoire consists of songs popularized by other performers. It was a new example, to me, of a phenomenon I’ve discussed before — the growing pluralization of attributive nouns, such as Yankees fan replacing Yankee fan. As with such phrases as jobs (instead of job) report, drinks (instead of drink) menu, and books (instead of book) editor, the covers band example is consistent with the trend of Americans (Koethe was born in San Diego) adopting British usage. Of course, plural forms have not been unheard of in the United States: for example, parks commissioner or Antiques Road Show. But more and more attributives have become plural; I actually have the sense that I had never before even confronted covers band.
This Google Ngram Viewer chart confirms that it has been rare in the United States, while (interestingly) roughly equally common as cover band in Britain.
In a sort of Woody Allen-Marshall McLuhan moment, I tweeted at The New Yorker copy editor Mary Norris, wondering about the use of covers in the Koethe poem. She responded:
Oldies station — a radio station that plays old songs — is indeed a longstanding formulation here. Maybe it’s a music thing?
That doesn’t appear to be the case. In a 2002 paper, the linguist Elisa Sneed refines the work of Maria Alegre and Peter Gordon in determining the circumstances in which plural attributives tend to be used. There seem to be two important factors. The first is “abstractness.” Sneed writes: “Something not easily imagable, such as a process (admissions), an action (assists), a thing (benefits), or something that is otherwise complex (dissertations) is abstract; something easily imagable and simple conceptually, such as pencils or flowers, is concrete” (italics added).
So dissertations index sounds okay; *flowers pot does not.
The second factor is heterogeneity in the head (final) noun of the phrase. Sneed gives the example of analyst as a head noun that promotes “diversity among the entities denoted by the internal noun” and pile as one that highlights homogeneity. So we might say weapons analyst but weapon pile, as well as cookie jar and sock drawer.
She provides this nifty predictive chart, explaining, “Compounds that most closely meet the requirements for abstractness and heterogeneity will be perfectly acceptable, like admissions department. However, as we move away from the ideal in either dimension, the compound becomes less acceptable. This is illustrated by the difference between antiques dealer and antiques collector in the iso-acceptability diagram, where the latter is farther from the ideal.”
Three other wrinkles. First, irregular plurals tend to be more acceptable than regular plurals as attributives. We might say mice droppings but never *rats droppings. Second, as noted by David Crystal, the plural is often used in cases when meaning might otherwise be ambiguous or misleading. Thus, in baseball, a batter who doesn’t have enough power to produce doubles, triples, or home runs is a singles hitter. To call him a single hitter might mean that he’s just one hitter, or that he’s unmarried. Finally, the plural is used in cases when a possessive apostrophe is understood, such as farmers market or the street in Philadelphia where you go to buy a wedding ring, Jewelers Row.
I haven’t found a source that discusses, much less explains, the British preference for plurals even when Sneed’s criteria are not met, or the recent American tendency to adopt these expressions. Going back to the original example, there definitely is a sense of heterogeneity — it wouldn’t do to play the same song over and over again. But one has a concrete rather than abstract sense of the repertoire, be it “Proud Mary” or “Get Off of My Cloud.” Yet John Koethe chose and insisted on covers band. It is a puzzlement.
The one thing I’m fairly certain of is that the plural trend will continue, and that the tendency will be to call it the plurals trend.
notoneoffbritishisms.com 
As a fan of the New York Yankees I would definitely be a Yankees fan, A Yankee fan would be a fan of an individual player surely?
…or a fan (of whatever or whomever) who’s a Yankee.
As a Brit – admittedly a wrinkly one – I’m not familiar at all with “covers band”. There are bands that do Beatles covers, for example, but they would be a Beatles “cover band”. But then I’m a child of the 60s, which is a long time ago………
Aome of the plurals make sense as descriptive Yankees is the name of the team not the Connecticut Yankee of Mark Twain., Jobs Report is surely about more than one job. Drinks menu could go either way. Book editor seems to feel right as an editor would probably actually edit only one book at a time. Still covers band feels odd.
The usual term in the US is “cover band”. But “covers band” doesn’t sound that odd. After all, a “cover band” would be glossed as “a band that plays covers”.
Note that Bill’s example, above, of “There are bands that do Beatles covers, for example, but they would be a Beatles ‘cover band'”, is incorrect. A band that specializes in covering just one band’s songs would not be called a cover band. That’s what’s called a “tribute band”. A cover band is expected to cover a wide array of bands’ songs, usually in a variety of styles.
Cameron, I checked with my wife and she agrees with you. “Bjorn Again”, for example, is an Abba tribute band, not an Abba cover band. But neither of us would ever say “covers band”.
She also thinks that grown men – it’s usually men, apparently – discussing whether “cover” should be singular or plural is the modern equivalent of “angels on pinheads”. I told her that’s exactly right!
The Antiques Road Show is a ancient BBC programme so probably does not count as a purely American example.
In English we always say “mouse droppings”.
A covers band is just a band which does covers. I suppose just as a jazz band does jazz and a pop band does pop.
I love a good poem and that Fats Waller song.
Having read one of your links, I’ll say that the example given of 14-year-old boy or 100-yard sprint is correct English. If I saw 14-years-old boy or 100-yards sprint printed in a newspaper I would call it plain wrong.
We do talk about a cover record, usually shortened to a cover, but not a covers band. A cover group or band would be more like it.
The Yankees fan. Is that not because the team is called the Yankees and not the Yankee team? It means Yankees’ fan. A Yankee fan could mean something else, no? We talk about an England fan (of the England team), not an Englands fan…but a Beatles fan or a Stones fan.
Admissions and communications takes me to the American word accommodations which we call accommodation. I’ve never understood why the s on the end of that one. They also like longer forms in some cases where we have dropped them, for example, our government department of transport but their department of transportation.
Books editor. We mostly say editor rather than book or books editor. Newspapers have a page with the heading “Books”. Maybe it’s journalists’ shorthand for editor of “Books”, meaning editor of the “Books” feature or page.
When I was planning a new house, I said I wanted to have a book room, not a books room. (To call it a library would have seemed too grand or pretentious. It wasn’t a stately home!)
But I concede the drinks party, the drinks menu and the drinks trolley. Maybe Americans invite people for cocktails or to a cocktail party with a cocktail menu instead?
I do not believe we British have a preference for plurals but instinctively apply English variably as the sense and context dictates.
A ‘park commissioner’ is not the same as a ‘parks commissioner’, the former being respondible for one park, the latter a number of parks, but there may also be confusion with a general description and a job title.
Drink menu v drinks menu: depends whether drink is used as a collective noun. Drink in the UK, often is associated with alcohol; ‘drinks’ indicates a variety of alcoholic and non-alcoholic.
Antiques Road Show is a programme about antiques; Antique Road Show would be an old programme about roads perhaps.
I have never heard covers band, jobs report or books editor in the UK.
Perhaps there is some confusion here with plurals like Attornies General (correct) Attorney Generals (incorrect).
Except that the Oxford English Dictionary lists ‘Attorney Generals’ as the preferred or ‘better’ plural form.