Original sentence: Available introductory material includes methods for classical instruments such as the violin, clarinet and trumpet, folk instruments such as the harmonica, mandolin and banjo, as well as material for various types of guitar.This material often emphasizes styles such as classical, rock, blues, jazz and folk music
Edited sentence: Available introductory material includes methods for classical instruments such as the violin, clarinet and trumpet, folk instruments such as the harmonica, mandolin and banjo, as well as great deal of material for various types of guitar.This material often emphasizes a wide variety of styles, such as classical, rock, blues, jazz and folk music