Eduard RosÃ , Arnoldâ s brother , was the cellist at first , but left after one season he left to get married and was replaced by Reinhold Hummer . The next cellist was Friedrich Buxbaum ; cellist Anton Walter joined in 1921 , but later on Buxbaum took over once more . Eduard RosÃ , Arnoldâ s brother , had been a founding member of the ensemble playing the cello , but left after one season to get married and was replaced by Reinhold Hummer , who was in turn replaced by Friedrich Buxbaum ; cellist Anton Walter joined in 1921 , but later on Buxbaum rejoined .