The person singing the lead role in Lucio Silla was a castrato named Venanzio Rauzzini in his late 20s. Mozart was especially fascinated with him, and he wrote him a three-movement motet, 'Exsultate, jubilate,' which women sopranos generally sing these days. To both composer and artist the last movement was a bit of a show-off. Mozart gave himself the challenge of setting only one term for the entire campaign, "Alleluia." Rauzzini would have loved it with its fast-paced and amazingly catchy vocal line. This was first heard on 17 January; at the Theatine Church in Milan in 1773. Exsultate, jubilate, for Mozart, is an important piece and one of the few pieces he wrote before adulthood that has remained among his most popular works.

Washington initially protested enlistment of slaves in the Continental Army, but later he relented when the British emancipated and used theirs. On January 16, 1776, Congress allowed free blacks to serve in the militia. By the end of the war one-tenth of Washington's army were blacks.

Swan gave a working demonstration at The Newcastle Chemical Society meeting on 17 January 1879.

Lewis Latimer, employed at the time by Edison, developed an improved method of heat-treating carbon filaments which reduced breakage and allowed them to be molded into novel shapes, such as the characteristic "M" shape of Maxim filaments. On 17 January 1882, Latimer received a patent for the "Process of Manufacturing Carbons", an improved method for the production of light bulb filaments, which was purchased by the United States Electric Light Company. Latimer patented other improvements such as a better way of attaching filaments to their wire supports.

On January 17, 1920, the Eighteenth Amendment to the U.S. Constitution took effect and Prohibition lasted until the amendment was repealed in 1933. The amendment prohibited the manufacture, sale, and transportation of alcoholic beverages. Demand for alcohol naturally continued, the resulting black market for alcoholic beverages providing criminals with an additional source of income.