Answer
The answer is "Sadko", a musical tableau composed by Nikolai Rimsky-Korsakov in 1867. It is based on a Russian folk tale about a legendary gusli player named Sadko who makes a pact with the Sea King, leading to extraordinary adventures. Though sharing the title, it is distinct from Rimsky-Korsakov's later opera "Sadko", composed in 1896, which provides a more extensive and operatic treatment of the same folk tale.