Thelonious is a hipster mouse who cannot keep himself from taunting the cat of the house, but once Thelonious discovers a toy piano, he and the cat make some beautiful music together. Interest Level: K-3 Reading Level: 2.5 ATOS Book Level: 3.1 AR Interest Level: LG AR Points: .5 AR Quiz: 144827EN Lexile Measure: 670 Lexile Code: AD (Adult Directed).