I am making playlists for fitness walking. For "interval training" I'd like to be able to put just portions of tracks into a playlist. For example, I might warm up to one or two songs in their entirety, but then speed up for just 60 or 90 seconds, then slow it down for 3 minutes, then have another 60 or 90 seconds of a higher beats-per-minute song, repeat. . . . I'm new, and have figured out how to make playlists of various songs, but can't figure out if there is a way to put just part of a song into a playlist. Thanks.