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, except for the notes along the right-hand side of the page that are related to natural elements and accompanied by a drawing.
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.
It’s surprising how similar the solution of the worm screw and the movable cage are to the modern timpani drum. The only difference is the musician’s use of a pedal to tune it rather than a handle.