Many instruments with enharmonic keyboards were built during the Renaissance and Baroque eras. Most composers and performers who used these instruments are virtually unknown today. Among them are Johann Kaspar Kerll's teacher, Giovanni Valentini, who played a harpsichord with 77 keys for 4 octaves (19 keys per octave plus one extra C), and Friedrich Suppig, published one of the definitive works for an instrument with an enharmonic keyboard: the "Fantasia" of the "Labyrinthus Musicus", which is a multi-sectional composition that makes use of all 24 keys and is intended for a keyboard with 31 notes per octave and pure major thirds.