The left hand plays a duet a sixth below the right hand. While the right hand sings 'cheerfully' in D major, the left hand plays a tonic chord in F-sharp minor, creating a sense of incongruity between the two hands, which I believe is an interesting aspect. In measures 13-16, the major-key melody sung in measures 5-8 suddenly shifts to minor. Here, I was reminded of Schubert's Lied, 'Lachen und Weinen' (Laughter and Tears). The fluctuating emotional state, expressed as 'I don't understand my own heart, laughing in the morning but crying in the evening,' is conveyed through a sudden modulation. In this 'Cheerful Song,' however, the four-measure modulation is as if, while singing cheerfully and joyfully, one suddenly recalled something unsettling. From measure 17, the theme is restated in the major key at f, as if nothing had happened.