Aho is a very approachable and highly skilled contemporary composer. His work reflects his tuition by Rautavaara and his admiration for Shostakovich, though he has his own distinct voice, so it's not surprising that his music is so attractive. His musical language is often quite "romantic" and in this most public of works we hear an even more conventionally post romantic voice.
This symphony, as Kalevi Aho works go, has been much hyped and praised. Its premiere, on the slopes of Mount Luosto, was rated as one of the highlights of the year in Finland - I'm not sure what that says about Finland but any country that produces so much musical talent with such a small population must be doing something very right.
The symphony is a very ambitious work and superbly recorded by BIS. My reservation here, and it is not a criticism of BIS, is that you probably need the full surround sound to get the most out of it. I would love to hear this being performed at the place of its premiere and for where it was intended. Two orchestras are at work and their placement cries out for the surround sound (lucky you if you've got it).
Under normal conditions you may lose some of the nuances and detail. Aho realised the logistical difficulties for such forces and didn't write too much intricate or over complex counterpoint that could get lost in the mix. As I said, this isn't a criticism of BIS because, even with these nuances lost on a simple stereo system, this still sounds like a very vivid recording - typical BIS, in other words.
The symphony is in four movements that might be taken equally as four separate tone poems bound together. The opening "Shamans" with pounding drums is impressive indeed. The second movement depicts the move from the endless dark of the arctic winter to the first burst of sunlight with the changing seasons. That might sound like the cue for some vivid music but, in truth it all sounds a little too bound by convention. If you want a vivid depiction of the Finnish night sky try Saariaho's "Lichtbogen" - a depiction of the Northern Lights, or her "Winter Night Sky" from her "Orion" suite.
The third movement "Song of the Fells" includes a vocalising duet which again a little too bound by convention, but the storm that is depicted in the finale represents a welcome shift and brings the work to a satisfying conclusion.
I think Strauss's Alpine Symphony provides a close analogy. Whatever analogy you prefer
it is essentially a symphony made up from a collection tone poems.
In short; it's an impressive piece of recording of a remarkable project on the composer's behalf and BIS but it is certainly not Aho's best work. Still highly recommended but I suggest, for starters that you look at his magnificent Symphonic Dances, Fourth Symphony, Rituals, Flute Concerto and others - all superbly recorded by BIS - what a lucky composer he is to have a recording contract with them.