But not all of his music is well known. Leif Segerstam and the Turku Philharmonic Orchestra have been devoting time and care to recording some of the lesser-known orchestral works, principally incidental music, in a series of releases for Naxos. I covered one a short while ago (use search box above to find that) and now another: Swanwhite -- Complete Incidental Music and others (Naxos 8.573341).
The album devotes much of its time to "Swanwhite" (1908) and "Odlan (The Lizard)" (1909), each running nearly a half-hour. Then there are the brief music and narrative sequences "A Lonely Ski Trail" (1948) and "The Countess' Portrait" (1905).
We get some very attractive tone painting from the early stages of his career for the most part. The influence of Grieg can sometimes be discerned, otherwise this is proto-Sibelius that speaks on its own terms. He most certainly shows his brilliant orchestrational genius in embryo here. And the music sings out dramatically and attractively.
The performances are quite good, sensitive to the sweep of Sibelius's grand natural gestures. The music may not be quite at the high point of mature Sibelius, so perhaps this is not the place for the listener to start with the composer if one does not already know him. But for those convinced Sibeliphiles it is all very nice to hear, something you will want to have.