Mix buss compression is a great way to add a little bit of excitement and glue to your mix. Some people like to slap it on the master buss after they have mixed it (Ryan West for example, whose credits include Jay-Z, Eminem, Kid Cudi, Maroon 5, T.I., Rihanna, and Kanye West). And some engineers like to slap a little bit of compression on in the beginning and mix through it. I don’t think there is a right or wrong way when it comes to when to put it on.
As we just saw, one musical principle that has reverberated throughout time and across continents and cultures is theme and variation. To revisit that classic example, here’s the theme from Beethoven’s “Symphony No. 5” and the first variation of it, displayed in Ableton Live’s piano roll. The simple shifting of the notes downward is very effective.