Among these heterogeneous drawings appears a paragraph accompanied by the drawing of the two flutes. Although the size of this “music box” – drawn on a folio entirely dedicated to mechanical studies – is very small, there is enough information to realize the design. The drawing shows two Glissando Flutes – instruments that let the player pass from one note to another in a continuous way, without tonal intervals. Leonardo writes:
These two flutes do not produce sounds at intervals but rather in the manner of the human voice. This sound is produced by moving your hand up and down, as on a trumpet or a flute. You can also produce sounds at tone intervals of 1/8 and 1/16, and any other sound you like.