Conversation so far:
Is Sonata Arctica's Unia and The Days of Grays a musical band?
Unia, is the fifth full-length studio album by the power metal band Sonata Arctica. The Days of Grays is the sixth full-length studio album.
Wsa the Sonata Arctica album, Unia a hit?
Who were the artist in the Sonata Arctica album, Unia?
Sonata Arctica album, Unia is the last album that features Jani Liimatainen, who was later replaced by Elias Viljanen after the album was released.

Question: Who was their lead singer?
Self-contained rewrite: Who was Sonata Arctica's lead singer?