con·cert 
(kŏnsûrt′, -sərt)
(kŏnsûrt′, -sərt)n.
1. Music A performance given by one or more singers or instrumentalists or both.
2.
a. Agreement in purpose, feeling, or action.
b. Unity achieved by mutual communication of views, ideas, and opinions: acted in concert on the issue.
c. Concerted action: "One feels between them an accumulation of gentleness and strength, a concert of energies" (Vanity Fair).
v. (kən-sûrt) con·cert·ed, con·cert·ing, con·certs
v.tr.
1. To plan or arrange by mutual agreement.
2. To adjust; settle.
v.intr.
To act together in harmony.
[French, from Italian concerto, from Old Italian, agreement, harmony, from concertare, to bring into agreement, possibly from Vulgar Latin *concertāre, to settle by argument, from Latin, to debate : con-, com- + certāre, to contend, frequentative of cernere, to separate, decide by fighting; see krei- in the Appendix of Indo-European roots.]