When using Sony Sound Forge, it's easier to mix different songs. Just download the software now and start your craft. Then, select the songs to be included in your project. Open each with SSF. The song will appear as a graph on your screen. Cut the part that you want by highlighting that part then CTRL-V. Open the other songs and do the same procedure. There are also other effects that can be applied on your music mix. Moreover, you can add other sound effects like thunder. Mix to enjoy your self-made music.