From the Super Mario Wiki
 Paper Mario
During the events of Paper Mario, she becomes depressed after the kidnapping of Princess Peach, rendering her unable to sing. Mario has to bring Chanterelle music by having an item called Lyrics, written by Master Poet and have it to compose the item by Toad in the Desert as it changes into the item, the Melody; as the item helps Chanterelle reawaken her natural vocal ability. There is no clue given to where the composer lived; the lyrics says they must be taken to a composer "somewhere in the world." Luckily, Mario manages to give Chanterelle the completed composition. She sings for Mario beautifully and in tune. She then rewards Mario with an Attack FX D Badge. After that, Mario can ask her to sing the song again if he wishes to. She'll sing the song again for him how ever many times he wants her to.
She later appears with her two Toad instrumentalists, conducted by the Master Poet, in the game's credits. The song is also heard at the very end of the game with the "The End" screen for a while when Princess Peach and Mario are at the castle overlooking the fireworks.