Painful Frequency Burst

So, I eventually got so annoyed with this thing, I decided to consider fixing it. The theory so far is that my processor (being the lowest # of GHz for the new macbook) is being overloaded by the large number of tracks I have on my garageband song. I checked the activity monitor and it turns out so. So now I'm going to change all of my tracks into audio files, lessening the stress on the processor (and hopefully getting rid of that noise).

If any of you out there have experienced this painfully loud frequency burst, please tell me about your experience so that I can deduce this problem more efficiently.