He stated that he did not understand the requirement of other pianists to continuously reinforce their relationship with the instrument by practising many hours a day. It seems that Gould was able to practise mentally without access to an instrument, once going so far as to prepare for a recording of Brahms' piano works without playing them until only a few weeks before the sessions. Gould could play from memory not just a vast repertoire of piano music, but also a wide range of orchestral and operatic transcriptions. He could "memorize at sight" and once challenged his friend John Roberts to name any piece of music that he could not "instantly play from memory".