Botstein notes that music assumed a pivotal and permanent role in Einstein's life from that period on. Although the idea of becoming a professional himself was not on his mind at any time, among those with whom Einstein played chamber music were a few professionals, and he performed for private audiences and friends. Chamber music also became a regular part of his social life while living in Bern, Zurich, and Berlin, where he played with Max Planck and his son, among others. In 1931, while engaged in research at California Institute of Technology, he visited the Zoellner family conservatory in Los Angeles and played some of Beethoven and Mozart's works with members of the Zoellner Quartet, recently retired from two decades of acclaimed touring all across the United States; Einstein later presented the family patriarch with an autographed photograph as a memento.^[116][117] Near the end of his life, when the young Juilliard Quartet visited him in Princeton, he played his violin with them; although they slowed the tempo to accommodate his lesser technical abilities, Botstein notes the quartet was "impressed by Einstein's level of coordination and intonation."^[115]