Underground Tunnel - Invisible Sorrow is a music track that is featured in Castlevania (N64) and Castlevania: Legacy of Darkness. It is the background theme of the Tunnel.
An arrangement of this music appear as bonus track on the Castlevania: The Original Game Soundtrack album.
Castlevania 64 OST 29 - Underground Tunnel - Invisible Sorrow.
Castlevania 64 OST - 38 39 Invisible Sorrow