Four Seasons was sung by Iroh, with some of the crew playing instruments and dancing. Shortly after they finished the song, Admiral Zhao boarded the ship and took charge of Zuko's troop. That was the last time Iroh played with the crew.
Iroh's Tsungi horn theme is played throughout the series, but is usually played when Zuko is in distress or when there is some sort of tension. A notable appearance of this song was when Zuko became sick after freeing Appa. He was fighting his inner self and slowly realizing the difference between good and evil. He had higher spirits after his sickness, and was even optimistic of a better, simpler life with his uncle, but Azula promised his redemption if he helped her capture the Avatar and secure ruling over Ba Sing Se. He followed her, sending Uncle Iroh to jail as a traitor.
Leaves from the Vine was the song Iroh sang at the grave of his son. It's a very emotional song for him since his son died in a attempt to conquer Ba Sing Se. Even more emotional is the fact that Iroh was leading the Invasion. This episode was dedicated to Mako, the voice actor for Iroh, who died during the production of season two.
Iroh is in Jail for most of Season 3, and then off to take back Ba Sing Se with the Order of the White Lotus... not leaving much time for music. The last time he plays is on his tsungi horn in the final episode when everyone is together and safe in Ba Sing Se.