How do you get more than one audio line onto Windows Movie Maker?
No, you have only one audio line. What you can do is fudge things to give you three lines, since you have an audio track associated with your video, a separate audio track, and a narration track. So, take the video and add your first audio, then export this as a video with audio and re-import; import and add your second audio; finally, record your third audio on to the narration track. I think the narration track has to be recorded directly in to MovieMaker, and can’t be imported, but I’ve never tried. The alternative is to build up your audio in stages. It’s messy. Realistically, Windows Movie maker isn’t really intended for anything as sophisticated as multi-track work.
