The importance of improvisation for keyboard players only began to decrease in the early 19th century, despite the fact that it had been regarded as a crucial ability for every professional performer until then. Professionals had not necessarily needed an exactly notated score before, but by the early 19th century, an increasing number of amateurs among the bourgeoisie were learning to play the piano and required a large repertoire of music that was notated precisely. Czerny's contemporary Johann Nepomuk Hummel offers authors another prime example of why the first three decades of the 19th century may be regarded as a highpoint of piano improvisation. But compositional innovation was also influenced by improvisational practice, because the latter promoted opening up established schemata, freer progressions and more open formal concepts. There are numerous reports of piano improvisations lasting thirty minutes or longer during the Classical period, especially in the case of Beethoven.