An illusion that relies on the sound of the flute. Whoever hears it will be assailed by the vivid sensation that their limbs have been fastened with sturdy ropes, thus becoming unable to move about freely. Even with physical intervention from an outside force, the body is robbed of all mobility, and consciousness itself progressively fades away. At the same time, they are fed morbid hallucinations, which makes it also possible to run them down mentally. Given that the means of transmission is sound-based, it has a large range of effectiveness, on top of which it can be applied even without knowledge of the enemy's position, which makes for an exceedingly convenient technique. The genjutsu is ineffective if the opponent can't hear the technique.
After injecting himself with Tayuya's DNA, Kabuto gained access to this technique. Instead of her ordinary flute, he instead used a doppelgänger of Kimimaro to create a flute made of bone. Kabuto's version of this technique has the victim wrapped with snakes instead of ropes.
Mateki (魔笛) is the Japanese name for Mozart's famous opera Die Zauberflöte.
When Shikamaru Nara was caught by this illusion, in the manga, the flesh of his arm was melting off his bones; in the anime, his entire arm was melting, including the bones.