The main composer is Inon Zur
 

For those who don't know, he's behind the brilliant Dragon Age: Origins soundtrack.

FO4 main theme:


And I quite like it.

Me as well - can get the full hour on Youtube which I am listening to now - thanks for posting this as I hadn't heard it.

And erm Fallout 3. He 'aint no Kai Rosenkranz though :)

Yeah, I've never really been impressed with his work; standard Bethesda sound guy. not really a surprise. Jeremy Soule or Mark Morgan would have been a welcome change.

You can see Inon playing it in a video here when it was originally posted:

http://www.rpgwatch.com/forums/showthread.php?t=30739

I don't think much of this theme personally; too similar to F3+NV, with not near enough post apocalyptic menace and too much Bethesda edged "triumphalism".

"The Lost Mariner" track however, is an improvement for me at least:
https://www.youtube.com/watch?v=gOrisHFmMlg