In Avatar: The Last Airbender, Uncle Iroh is shown playing an instrument called a tsungi horn on at least two occasions. Iroh plays the tsungi horn in Avatar season 1, episode 13, “The Blue Spirit,” and again in the series finale – Avatar season 3, episode 21, “Sozin’s Comet, Part 4: Avatar Aang.” The name of the tsungi horn is mentioned in the season 1 episode “The Waterbending Master,” when Iroh’s nephew, Prince Zuko, refuses to play the instrument on music night. Aang gleefully attempts to play the tsungi horn in season 3's “The Headband,” while attending a Fire Nation school undercover, but it's clear that he doesn't actually know how to play.
Other notable musicians in Avatar include Chong and his wife, Lily, who appear in season 2's "The Cave of Two Lovers," and The Flamey-Os, a Fire Nation band that features a tsungi horn player, and appear in the season episode "The Headband." Though many of the musical instruments shown in Avatar exist in the real world – for example, The Flamey Os also feature a morin khuur (a Mongolian instrument also known as a horsehead fiddle) and Chong plays a dramyin (a Himalayan lute) – the tsungi horn is a fictional instrument that doesn’t have an exact counterpart in the real world.
The fictional tsungi (also spelled sungi) horn is wrapped over the player’s shoulder like a sousaphone but produces a sound more like a bassoon – a double-reed woodwind instrument. This is because the primary instrument used to create the sound of a tsungi horn is a duduk, which is an ancient Armenian woodwind instrument with a double reed. However, a second instrument also lent itself to the tsungi horn’s unique sound. Aang and Zuko both play the instrument, but Iroh, the beloved tea-drinking firebender, is the only one shown playing skillfully. Zuko is supposedly a gifted player but chooses not to perform and Aang, to put it gently, is not a skilled tsungi horn player. In Avatar, tsungi horn music was produced by “a music synthesis technique called convolution to impose characteristics of a trombone onto the duduk” [via Avatar Spirits].
Duo Jeremy Zuckerman and Benjamin Wynn, aka the Track Team, created the music for both Avatar: The Last Airbender and Avatar: The Legend of Korra. Avatar's score was heavily influenced by traditional Chinese music, but Zuckerman and Wynn used instruments from around the world to compose Avatar’s soundtrack. Most of these real musical instruments were used for the soundtrack or depicted within the show without significant alteration, but the duduk was modified with the sound of a trombone, giving Iroh a musical instrument that is uniquely his own.
In the world of Avatar, music is used for storytelling and entertainment, but it also has spiritual meaning and is used to enhance one's connection to the spirit world. Iroh is very spiritual and arguably the most musical character in Avatar: The Last Airbender - singing, humming, or playing his tsungi horn throughout the show. One of the show’s most emotional moments is in season 2's “The Tales of Ba Sing Se,” when Uncle Iroh sings a lullaby called “Leaves From The Vine." The episode reveals that Iroh is still grieving the loss of his son, and the song he sings is deeply moving. Iroh was once known as the Dragon of the West, but the death of his son, Lu Ten, broke him. Eventually, Iroh turned his focus to mentoring Zuko and found peace in the spirituality and creativity of music.