The designs on folio 175r of the Codex Arundel represent a rare case of thematic homogeneity and working order. In fact, they are largely tied to the invention of small musical instruments. These instruments should not be considered minor. On the contrary, they are quite innovative. The Stretch Drum, for one, could be considered a predecessor of the modern timpani drum.
By turning the handle, the musician could tighten or loosen the drum’s skin, thus changing the intonation. The traction was enabled by a cage, most likely made of metal, which passed along a screw, thus exerting force along the rim of the drum.