Otogakure

, called Oto for short, was Orochimaru's personal village, founded for the express purpose of collecting ninja for his experiments and his quest to learn all jutsu. In actuality, Oto is not really a village, but a group of hideouts and bases scattered throughout the Land of Sound and other countries. Three Sound ninja (Dosu Kinuta, Zaku Abumi, and Kin Tsuchi), under Orochimaru's orders, entered the Chunin Exam with the goal of killing Sasuke Uchiha. However, Orochimaru was actually using them as test subjects for Sasuke's power after Orochimaru gave him the Cursed Seal. Sound ninja use a diverse amount of jutsu. The Oto symbol is an eighth note.

Trivia

 * Despite not being one of the Five Great Villages, Orochimaru had been dubbed by fans as "Otokage", due to his powers being that to rival a Kage-level ninja.
 * With Orochimaru permanently sealed and Kabuto gone, it it possible that Otogakure was abandoned or destroyed. The village's real fate is unknown.
 * Although a village, Otogakure shouldn't be considered a true village, due to the fact it is a self-established village and was created by Orochimaru for his personal needs.
 * Otogakure isn't necessarily a true Hidden Village, but used as Orochimaru's personal hideout for conducting experiments.