This work of Op.34 began it life as a string quintet (completed in 1862 and scored for 2 violins, viola and 2 cellos). Brahms himself transcribed the quintet into a sonata for 2 pianos (in which form Brahms and Carl Tausig performed it) before taking its final form. Brahms supposedly destroyed the original version for string quintet, but published the Sonata as opus 34 bis.
