Рахманинов. That is the russian equvilent to Rachmaninoff. Some people choose to say or spell it Rachmaninov or Rachmaninow. The little B character at the end stands for the letter or sound V. However, in russian if this letter is used at the end of a word, it makes an F sound. Hence, the correct spelling and pronunciation of the name is "Rachmaninoff". Remember, this is the way Rachmaninoff had it spelled on his tombstone. So, if you've gone with the misinformed crowd and said "Rachmaninov", now's the time to change your ways.