Late 1400s
According to Polk, “The trombone had been further refined—the bell was less flared, producing a more covered, blended sound which was a timbre particularly effective for working with voices, and with zincks and crumhorns. We know that the Nuremberg family of makers, the Neuschels, was credited at the time with some basic redesign of the instrument, and they may well have had a hand in this development.”