Before & After video

Hi, I'm a web developer and was thinking of creating some simple before & after videos of sites I'm working on. For example, I was just kind of imagining something simple, like some video scrolling through the home page and maybe some interior pages with "Before" as a caption, and then ditto with the new site, with "After" as the caption. Maybe like 30 seconds or less, with some background music. Any suggestions on a free/open source video editing software platform that I could use for this, that's easy to use? Also, any suggestions on where to find free background music?

Thanks in advance!