In 1744 there was a concert at Faneuil Hall in Boston for the benefit of the poor; and Mr. Dipper, who was the organist of King’s Chapel, announces  on in the Boston “Post Boy,”  Feb. 2 , 1761: -

Mr. Dipper’s Publick Concert

will be To-Morrow the 3d of February; when  will be performed feveral pieces of Vocal and Inftrumental MUSICK, compofed by the beft Mafters; and many of them accompanied by two French Horns…
[Henry Mason Brooks, Olden-time Music; A Compilation from Newspapers and Books, Ticknor, Boston, 1888, p. 84]

Says Josiah [Quincy], e.g., under March 17, [1772]:
Dined with the Sons of St. Patrick. While at dinner six violins, two hautboys, etc. After dinner, six French horns in concert: - most surpassing music.  Two solos on the French horn, by one who is said to blow the finest horn in the world. He has fifty guineas for the season from the St. Cecilia Society.
[Sonneck, Early Opera in America, G. Schirmer; Boston, 1915, p. 51, (quoting Josiah Quincy’s “Journal of a Voyage to South Carolina, etc.,” 1772)]

Notice of a grand concert in Philadelphia, 1786: -

PHILADELPHIA, May 30.

On Thurfday, the 4th of May, at the Reformed German Church, in Race-Street, was performed a Grand Concert of vocal and inftrumental mufick, in the prefence of numerous and polite audience.  The whole Band confifted of 230 vocal and 50 inftrumental performers, which, we are fully juftified in pronouncing, was the moft complete, both with refpect to number and accuracy of execution, ever, on any occafion, combined in this city, and, perhaps, throughout America.
[Brooks, (1888), pp. 228]