The original name of Moonlight Song is Piano Sonata in C minor.
Beethoven's sonatas in this period are full of tentative practice, and he tries to re-evaluate the main creative principles of sonata form. In the traditional mode, sonata form often appears in only one movement, and it is usually the first movement, but Beethoven broke this mode. Piano Sonata No.14 in C minor is one of the works that classical music school began to transform into romantic music school.
Music evaluation
Few famous songs are as famous as this sonata because of the common name "moonlight". There are different opinions about the origin of the name "Moonlight", but the most common one is that the first movement of this piece was described by the German poet Ludwig Rael Stubb (1799- 1860) as "like a boat swaying on a lake illuminated by moonlight in Lucerne, Switzerland".
Beethoven himself called this work "Quasi una Fantasia".