Concertedly is the adverb twin of concerted: you do something concertedly when you do it in a planned, together way, not each person off on their own. The feel is the same as the adjective — a little formal, more at home in careful writing than in chat. Though actually, English uses the adjective far more. People say a concerted effort all the time; they reach for concertedly less often, when they want to describe how the acting was done rather than what kind of effort it was. It is not a music word. Nobody concertedly means “in a concert-like way.” If the sentence already has concerted in it, you usually do not need this -ly form as well.