How do I level the volume in a piece of music without creating white noise during silent/quiet parts

Question

It's actually the original Star Wars trilogy soundtrack. The volume swings by 25 db or more, even during the same track. You can't listen to it without riding the volume knob. That's not hyperbole, you actually cannot hear parts of it if the loud parts are at a safe volume. It's not a bootleg copy or anything; I bought the CD's. Pathetic that they haven't already done what I'm trying to do, if you ask me.
Raising the volume of my sterio doesn't create white noise, so it seems like I should be able to duplicate the effect somehow, probably with some kind of dynamics processing. Classic Soft Knee, for example, has the white noise problem. When I used it in the talk radio business, it would also amplify the speaker's breaths. I've fiddled with it and tried to come up with my own settings without success. Maybe I need a different tool entirely?
I'm doing this for my son. He's 5 and loves Star Wars and loves listening to the music in the car wherever we go. Thank you for any help you can give!

Answer 1

My first, only slightly tongue-in-cheek reaction is to say, well done to the manufacturers of the CD!!  To actually allow the "full" dynamic range of the original to be released on CD!!
Sorry, I know that is not what you wanted to hear, but it is such a pleasant change that I couldn't resist commenting on the fact that the CD manufacturer actually does NOT want to "homogenise" the dynamic levels.  However, I realise this does create a problem for you in the circumstances of wishing to play the CD in your car.
You are correct, IMO, to be looking at the use of compression to reduce that dynamic range, though your talk of "white noise" is concerning.  Certainly the effect of compression is to reduce the dynamic range by, as it were, "decreasing the level of the loudest and increasing the level of the quietest parts"; there is a danger that increasing those quietest parts COULD increase the "noise" but I suspect the CD was recorded in pretty near "ideal" conditions, i.e. the noise floor was so far below the quietest signal that raising the level of that signal will minimally increase "noise", if at all.