A mistake that led to the death of Uzza, the son of Avinadav. King David's mistake was to bring the Holy Ark up to Jerusalem in a wagon. This week's Parsha tells us that the reason Bnei Kehas did not receive any wagons from Moshe was that they had no need of them. The Bnei Kehas were charged with carrying the Holy Ark on their shoulders. It was never to be moved around in a wagon.
Music exists in a limited system, encircled by the strictures of tonality.
Every octave, it essentially repeats itself. A note outside the scale is an excruciating impossibility. Fingernails on a blackboard. A violation beyond the boundaries of the musical sphere. Like a circle outside of which nothing can exist, music is a fixed system.