Kappei sings in the following songs as Usopp for the soundtracks and specials in the anime One Piece.
Furenzu (Friends) A Chopper and Usopp song
Samba Bomber Akuma No Mi (Samba Bomber Devil Fruit)- A group song
See Moon See you- A group sog
Usoppu no Hanamichi (Usopp's Flower Road)- A Usopp image song.