I have two versions, different artists, of the same song, both are about 4.5 minutes long. I have about 4.5 minutes of unrelated video and want to begin the video using one artist's version of the music and end the video with the other artist's version. The first would phase out as the second phases in without missing a beat or having a clumsy obvious transition from one artist to the other. The end result would be to have 4.5 minutes of video beginning with one musical version, ending with the second musical version with a smooth transition somewhere in the middle.