This instructable is the art of taking more than one melody or beat and putting them together to create a whole new song. These new songs are sometimes called "mash ups." However, mash ups are different in the sense that they utilize both songs to the same melody. Or the words from one song to the melody of the other. Mash up songs are usually very similar in chord progression, and the beats sync together. What this instructable is about, is overlap, which is different from mash ups. Overlaps take several songs and just lay them over top of each other until they sound good. Unlike mash ups, overlaps can use any song at all. They don't need to sound similar, they just need to sound good together. You can always go back and change the songs if you aren't happy with the sound.
The first step is to find a song with a good beat. The easiest way is to go on youtube and just start searching songs. I used "What in the Butt" for my base line, but don't think that you are limited to this song. You can use any song you want, as long as the drum beat is prominent in this first song. Instrumental versions always seem to work better, but if you can't find a version without words, just lower the volume enough so the words are behind the beat. I used Adobe Premiere to edit my over lap, but Windows Movie Maker is okay for this purpose as well. Bear in mind that Windows Movie Maker is not very cooperative when it comes to music, so i recommend Premiere. To get the music, i went on youtube and copied the URL for the song, then converted it to a mp3 using this site. http://www.youtube-mp3.org/
Step two is to find the basic melody. You're going to want this melody to compliment the beat you previously laid down. If it doesn't, you have a couple options, you can either speed up or slow down your melody to match the beat, you can speed up or slow down the initial beat, or you could find a different song. Sometimes it takes a lot of trial and error to find songs that compliment each other. I find piano melodies work best here, as they're usually consistent throughout the song. It took me several tries to get it right, or to at least to something that i liked. I used "Safe and Sound" for the final product, but again you are in no way limited to this choice. In fact, you could overlap more of the same type of melody. If you wanted to create an overlap with multiple piano melodies, you could. You would just skip step one.
Step three is to find a second melody to compliment the first. I find guitar rifts work the best here. The overlap melody is usually slightly fast, or slight slower than the first, and has to compliment the original beat laid down as well. This again, may take some trial and error to find one that works. I used "I Won't Give up" but slowed it down to compliment the melody of "Safe and Sound." Give your over lap a listen as many times as it takes to get it right.
This is the editing step. If you aren't happy with the way your over lap is sounding at this point, play around with the editing options. Try slowing down one song and speeding up the other. Increase the volume of the beat, and try to get a feel for when the melodies should come in. It's all a matter of what you believe sounds good. If your overlap isn't what you want, try a different song. Switch out the second melody first, and if you're still not happy, change the initial melody as well.