Indeed she did not really suspect the visitor, who was one too ingenuous in his nature to preconcert so subtle and so wicked a scheme.
-- Anthony Trollope, Dr. Wortle's School
If personal accidents, and accidents so trivial, could, to any serious extent, be amongst the causes of war, then it would become a hopeful duty to preconcert personal combinations that should take an opposite direction.
-- Thomas De Quincey, The Works of Thomas De Quincey
Though today concert is most often a noun, it was usually used as a verb in the 1700s typically in the sense of "to bring together" or "to arrange." Preconcert thus meant "to arrange beforehand."