From a Q&A column in the Times:

While watching a televised promenade concert I was irritated to hear the presenters constantly refer to Brahms’s (Brahmses) symphony. I would always style it Brahms’ (Brahms). Who is right?


It was formerly customary, when a word ended in “s”, to write its possessive with an apostrophe but no additional “s”, eg Achilles’ thews. In verse, and in poetic or reverential contexts, this custom is retained, and the number of syllables is the same as in the subjective case, eg Achilles’ has three syllables, not four. Jesus’ or of Jesus, not Jesuses. But elsewhere we now add the “s” and the syllable, St James’s not St James’ and Jones’s children. Personally, I would treat Brahms like Jesus or Socrates, Brahms’, sic. But either is possible. (Brahmses is naff.) But let us be tolerant of different tribes.