Piano Sonata No. 21 in C Major, Op. 53 "Waldstein" - Beethoven: Piano Sonata No. 21 in C Major, Op. 53 "Waldstein": II. Introduzione. Adagio molto (C大调第21号钢琴奏鸣曲，作品53“华尔斯坦” - 第二乐章 引子 - 很慢的柔板)