John L. R. Jennys is first listed as an active member of the musical trade in 1865 as a partner with Laurence Cummings in the firm Cummings & Jennys. Their firm was located at 233 East 21st Street, New York City. This partnership only last for four short years. In 1869, John L. R. Jennys entered into partnership with his son, John Jennys Jr., to form the firm of “Jennys & Son”.

The firm advertised itself as “manufacturers of grand, square and upright piano-fortes”. According to early advertisements, the firm won high acclaim for quality and craftsmanship. Among their successful patents was their “Patented Agraffe Treble” which allowed higher tension and greater brilliance in tone for high-end treble strings.  Jennys & Son went out of business in 1872, and their instruments are exceedingly rare today.