Giovanni Battista Sammartini was an Italian composer, oboist, organist, choirmaster and teacher. He counted Gluck among his students, and was highly regarded by younger composers including Johann Christian Bach. Sammartini is especially associated with the formation of the concert symphony through both the shift from a brief opera-overture style and the introduction of a new seriousness and use of thematic development that prefigure Haydn and Mozart. He is often confused with his brother, Giuseppe, a composer with a similarly prolific output (and the same first initial).