Coming to New York City early in 1857, his first assignment was to make a verbatim report of the Harvey Burdell murder trial.
Soon afterward, in connection with other court reporters, he set to work to simplify the existing systems of shorthand, and the fruits of their labor, as finally shaped and put into practice by Munson, were presented in his Complete Phonographer (New York, 1866), to the preparation of which he had devoted three years of labor, and tested it by seven years of practice.
He also reported the Henry Ward Beecher trial for the New York Sun, without assistance, during the six months of its continuance.
The report on the trial ran seven and a half columns of agate type per day.
Munson later went to work perfecting a typesetting machine that he had invented, which, being operated by means of a prepared ribbon of paper, automatically set a column of corrected, justified, and leaded type.