When Sebastian Tute finishes giving his introduction lesson, the player will be able to play Twinkle, Twinkle Little Star with the Tutes.
They appear later in the game for various reasons. The main one is when the player is doing jam mode alone. They will serve as the other members of the band he is in, unless if the player turns them off.
They will also teach the player how to play certain instruments during the mode Jam Mastery.