Sound Four

The Sound Four were Orochimaru's elite bodyguards. (Sakon and Ukon were counted as one entity, due to their kekkei genkai). Each was given a cursed seal by Orochimaru. Kimimaro was also a part of the group for a short time, since he was stronger than all four combined, thus renaming the group to Sound Five. However, an unexpected illness prevented him from participating normally. All five repeatedly referred to their opponents as "trash".

When Orochimaru sent the Sound Four to bring him Sasuke Uchiha, they were all systematically killed by Konoha and Suna ninja. Jirōbō was killed by Chōji, and Kidōmaru was killed by Neji, though the Konoha ninja suffered heavy injuries. Ukon almost killed Kiba, and Tayuya almost killed Shikamaru, but both were stopped and killed by Kankurō and Temari respectively. Kimimaro, after being sent as back-up, almost defeated Rock Lee and Gaara, but died from his illness during the battle.

Sometime before the Fourth Shinobi World War, Kabuto Yakushi took Sakon's Attack of the Twin Demons ability, in which he further used to absorb the abilities of the entire Sound Five, allowing him to use all of their skills against Sasuke and Itachi.

In the anime, the entire team was reincarnated by Kabuto to serve as a diversion in order to slow down the remaining Allied Shinobi Forces, while he prepared his trump card.

Abilities
Despite being young, all four of them are strong enough to become Orochimaru's bodyguards, and were all talented with barrier and sealing techniques. Shortly after their introduction during the invasion of Konoha, they used Four Violet Flames Battle Encampment to create a box-like barrier, that causes anything that touches it to burst into flames. When the group later fetched Sasuke, they used the Four Black Fog Battle Formation and Dark Sealing Method to protect Sasuke from harm. As the group later rested, they set up a Barrier Encampment Method. Each member of the Sound Four also had a cardinal direction associated with them; this was probably a reference to their positions when performing techniques as a group: Jirōbō of the South, Kidōmaru of the East, Sakon and Ukon of the West, and Tayuya of the North.

As with most of his powerful followers, Orochimaru branded then with different cursed seals, which greatly enhanced their individual abilities.

Trivia

 * The recurring symbol on the Sound Four's tunics was the yin-yang, though the yin (black) was missing. The missing yin represented imbalance, alluding to their evil natures and to that of the seals, preventing harmony in life.
 * Jirōbō and Sakon (and Ukon) specialised in close-quarter combat, while Kidōmaru and Tayuya specialised in long range combat. Kimimaro was balanced in both types.
 * Each member of the Sound Four tends to have a flaw in their personality that slows down the team: Jirōbō gets hungry and stays behind to feed, Kidōmaru tends to play around with his opponents if they interest him, Sakon can easily lose his temper and showcases the fact that he is the strongest of the four by not stopping until his opponents are dead, and Tayuya has a "doesn't want-to-lose" mentality.
 * Kidōmaru was the only member to wear an Oto forehead protector.
 * The Sound Four were playable characters in Naruto: Gekitō Ninja Taisen! 4, but they only appeared with the Second Stage of the Cursed Seal. Later, the Sound Four were playable characters in the Naruto: Ultimate Ninja 3, 4 and 5 with both regular and Cursed Seal forms playable.