An Admission: There Was A Fifth?

This morning, while reading up on Russian composer Pyotr Ilyich Tchaikovsky, one of my all-time favourite composers, period, I learned of "The Five" — or "The Mighty Bunch", the literal translation of "Могучая кучка", the original Russian. This fan of a certain school ("Simon and his big Russian music") was more than familiar with four of the five: Modest Mussorgsky, Nikolai Rimsky-Korsakov, Alexander Borodin, and César Cui.

There was a fifth, a composer I was not familiar with, even by name, and he was the leader of this gifted group: Mily Balakirev

Then there's the "Belyayev circle"....