What piece of music is played at the start of Sibeluis Six?

I have used Sibelius Six many a time, and it Always starts with that particularly nice piece of music. I like it so much that I would like to listen to it some more, but I cannot figure out what piece of music it is from.

So I would like to know, what piece of music is played when Sibelius Six starts up?What piece of music is played at the start of Sibeluis Six?
Yup. Here it is in context: http://youtu.be/V7W1oiu-nrs?t=5m24s . For the full symphony, start here: http://youtu.be/pnWAbM-fHD0



(I should say that I just learned something! I assumed someone on staff wrote it for the program.)What piece of music is played at the start of Sibeluis Six?
Sibelius: Symphony No. 6 Op. 104