Liszt once said that Mozart composed more bars than a trained copyist could write in a lifetime. One of the world's most enduringly popular classical musicians, Mozart had a profound influence on Western music and on his contemporaries such as Beethovenand Haydn. Johnson focuses on the importance of Mozart's music, uncovering his wondrous output of composition and his gift and skill with instruments. For example, no sooner had the clarinet been invented and introduced than Mozart began playing and composing for it.