Tangerine! analyses your songs to create playlists of similar songs. The app analyses your songs by calculating the beats per minute and the intensity of the beats. It uses that criteria to establish which songs are similar. Many people use Tangerine! to create exercise or relaxing playlists.
When you first launch Tangerine!, it will scan the songs that you have on iTunes and it will then analyse them. Once this is done, you can sort them by beats per minute or intensity. You can manually create a playlist by dragging songs to a timeline, or you can have the application do this for you. If you opt to have the app do it, you can set the minimum and maximum beats per minute and the intensity and all the songs that match those parameters will be added. The good thing is that Tangerine! tells you how many songs match even before you proceed to the next step.
When you are done creating your playlist, you can easily save it to iTunes. Before you save it, you can of course, play the songs and change their order. You can also double the BPMs for each song.