Stephen will no doubt want to refine this
explanation as well.
An obvious example of a variant spelling in the title
(composer) field is Tchaikovsky. That is now the
accepted transliteration of his name from cyrillic,
and Kelly spelled it that way about 50 times, but he
spelled it ‘Chaikovsky’ about 1500 times.
It was also common to spell any Russian surname
that ended ‘ov’ as ‘off’ such as Rachmaninoff