Complex sentence: The work began life as a string quintet (completed in 1862 and scored for two violins, viola and two cellos), later evolved into a sonata for two pianos (in which form Brahms and Carl Tausig performed it) before taking its final form.
Split into simpler sentences: The work began life as a string quintet (completed in 1862 and scored for two violins, viola and two cellos). Brahms transcribed the quintet into a sonata for two pianos (in which form Brahms and Carl Tausig performed it) before taking its final form.