Complex sentence: The quartet is named for the theme of the second movement, which Schubert took from a song he wrote in 1817 of the same title, and which bears a substantial resemblance to the slow movement of Beethoven's Symphony no.7.
Split into simpler sentences: The quartet is named for the theme of the second movement, which Schubert took from a song he wrote in 1817 of the same title. This theme bears a remarkable resemblance to the slow movement of Beethoven's Symphony no.7.