I wonder if this is possible? Well, considering I left my PC alone for 20 minutes and someone changed the dragon attack music in Skyrim to the Guile theme, I suppose it's doable in Oblivion.

How can I replace the Oblivion soundtrack with my own music, or music from my music library? And is there only a certain amount of songs I can have in the game?

Sorry if this isn't the right place to post this. I don't think this would be classed as a mod, but maybe I'm wrong.

This is done by copy/pasting mp3 files into one of Oblivion's music folders. Oblivion's Music folder is located inside the Data folder (Oblivion>Data>Music). Inside the main Music folder are five subfolders: Battle, Dungeon, Explore, Public and Special. Drop your mp3 into one of these subfolders and you should be good to go.

This will put your own music into the rotation. If you want to completely replace Bethesda's music you will need to take an extra step. I think the easiest way to do this is to take Bethesda's files out of their folders and store them in a different location on your computer. Later if you change your mind you can always move them back.

So I could have music I added in addition to the music already in the game? Hmm, not bad.

If I move the files somewhere else, could it cause any issues?

Nope. The game doesn't care which music files are in its folders, or how many there are. It doesn't make any distinction between your mp3s and the original mp3s.

You can put in as much or as little as you like. I've had as much as five hour's of my own music. These days I usually just put in one or two tracks that I really like. It's up to you. The system is very flexible.

Ah, good. But there's one issue, how do I get to the music folder again? I looked on YouTube for the answer but it says I need to look in the Steam folder, for which I need Steam. :/ I could get it, but I don't really care for it.