In this strip Lucy once again appears to react to the music Schroeder is playing. In the first movements of Classical sonatas, composers traditionally wrote two main melodies: the first, called the "masculine" theme in the 19th century, was loud and outgoing; the second, because it was soft and contrasting, was labeled the "feminine" theme. Here Schroeder is playing the feminine theme, which can indeed be heard as beguiling, in other words, "amusing, charming, delightful."
The music in panel 1 is measures 64 and 65 and the first note of 66. The Pathétique Sonata, also in the key of C Minor,
is one of Beethoven's most serious works.