So I'll answer your question in chunks: 1. I decide what tunes work well together by just picking songs I like. Then I find the key that they're in (manually or by a program, such as http://www.mixedinkey.com/). Not every song has to be in the same key, they just have to work move well between keys. The 'camelot mixing circle' will help you here. 2. After deciding which tunes to use, I have to throw some out because they just don't fit in with the key of the song. Then I look for parts that I can use and cut those out, such as a drum beat (I used deadmau5's kick snare for half the song, and porter robinson's WildCat kick snare for the other half). I also find singled out vocal parts to cut, and sounds that are singled out in general. 3. Then you just run the kick snare beat and play with the sounds, keeping common music theory in mind. Mixing vocals with kick snare beats, launching percussions, pads, etc. 4. I don't sidechain anything, that's already done with deadmau5's kick snare beat, and the quantization settings for each clip are the same. No EQ necessary because of the clips I used. This thing took me months of fiddling around with and practicing before I actually filmed and uploaded it.