Rippin doom music

How legal it is to take eg. doom 1 music and use it in doom 2 pwad?

People have been doing that for years, and nobody ever received any C&D or anything. Same applies to Heretic, Hexen, Descent, etc.
So unless you're asking money for your mods, you should be fine.

I believe it was resolved at some point that any doom asset can be used on either doom game completely legally because if the license or something saying so.

At least I seem to remember this being the case when I asked this question awhile ago.

@Rayzik: I don't believe that's true, actually quite vice versa. For example, the Doom 1 mapset KDIZD was, after a consultation with a representative from idSoftware, forced to remove all Doom 2 content and replace it with content made from scratch.