Kosh asks Sheridan to meet him at a strange, secluded place. He then asks Sheridan to enter a room. There is a hooded figure in there, and when Sheridan pays him with his rank badge, the figure and many others start singing.
The scene is from season 2, episode 14, and is called One Moment of Perfect Beauty (from a line spoken by Kosh in this scene). The episode is There All the Honor Lies.
Who are they? The only guess I have is that they are Pak'ma'ra because Emperor Vir tells a story years later about Pak'ma'ra singing so beautifully that even ambassador Londo is moved to tears. Vir said it was the most beautiful sound he ever heard, full of sadness and hope and wonder and terrible loss.
Does the novelization or any related stories mention who sang in this episode?