These days, we usually hear the word concerted as part of the phrase, concerted effort, and it seems to be used generally to mean intensive, or vigorous. Properly (or, at any rate, historically, for all you anti-prescriptionists out there), concerted means done in concert; co-operative; mutually contrived, undertaken, or performed.
American labor law preserves this meaning in the phrase, concerted action, meaning common action by workers for their mutual benefit or protection. In order for a worker to be protected (supposedly) against reprisal by the employer, his or her action must be concerted: it must be performed in concert with other workers, not by one worker alone.
Of course, in concert these days most often means, in “live” performance (as opposed to being recorded in the studio), so that we get stand-up comedians performing “in concert” by themselves.
I won’t go so far as to say that it’s wrong to use concert (or, for that matter, concerted) that way; but I do say that it’s best to keep words comfortably close to their historical meanings. Language evolves, and all that; but in an age in which millions of paid praters generate verbiage for hire, and innovation is valued for its own sake, the accelerated metamorphosis of the language may take on the character of metastasis, and become a thing to be resisted. (When that’s the case and when it’s not is a topic for another day.)
As things stand, concerted is in danger of becoming what I’ll call an eke-word—i.e., a word like eke, which has lost all contact with its historical meaning. Eke, once upon a time, meant to augment, to supplement. The phrase, to eke out a living, meant to supplement one’s income by some collateral activity, as in,
The poor curate eked out a living with a monthly column on gardening in the local newspaper.
In other words, the curate made a living—from being a curate—and he supplemented that—he eked it out—with what he received for writing for the paper.
Today, however, almost nobody uses eke to mean augment. (By the way, eke and the aug- in augment both probably come from the same Proto-Indo-European root, aug-, meaning, to increase. Compare German auch, Dutch ook, both meaning also.) These days, eke means something like to squeeze, to extract with difficulty, as in, “Carolina eked out a win over U.Va.” Maybe it’s because eke sounds like squeak, I don’t know.
What I do know is that eke is never going back to meaning supplement in ordinary speech: it’s almost completely detached from its historical meaning, and only language nerds like me even remember what its historical meaning was. Concerted seems to be headed the same way, but maybe there’s time to save it. Anybody want to save it?