How can I remove music from memory and make it by real sounds in the videos?

I’m not entirely clear on what you’re asking, and which tools you’re using with your iPhone.

Music doesn’t exist in memory, save transiently.

Music is stored in files, and those using any of various formats.

Music can be added to or dubbed to movies while editing the movie while using video-editing tools such as iMovie.

That would depend on which app or which plug-in you are using. iMovie can create slideshows, as can other apps.