How would i do this?

I think you go into the assets in .minecraft (I hope you understand me) and open a texture pack from something else that doesn't replace sounds, then add the music and sounds to either the assets folder inside the texturepack, or outside the assets folder in it. Hope I helped, if it sounds like I'm speaking another language I will clarify.

Um... Search it up on YouTube and if you can then look on the web and if you still can't then idk I feel bad for u..... Your one of my subscribers!!!!!!!! Thank you lol