iTunes Stuttering (No apparent causes)

I am currently running OS X Yosemite and iTunes 12.1, and have been doing so for a while. I have noticed that every few songs I play in iTunes, one of them will be full of 'stutters', or where iTunes stops playing for a second, then resumes about 2 seconds later. At least 20 of these occur in a song. I am running a 13" MacBook Pro (Non-retina) from Late 2012, 500GB with 8GB of RAM that I have upgraded myself. This problem has happened for a while, on previous systems and before I upgraded the RAM. I have checked Activity Monitor for any issues with RAM or increased paging but nothing shows up. The system cannot detect any kind of failures iTunes may be experiencing, and there are no signs whatsoever of any problems. I am not even doing anything remotely strenuous when the stutters occur, often my laptop will only have iTunes open and be otherwise idle. How can I fix this? And is it a Hardware or Software problem?