rMBP - Screen Freezing and Audio Stuttering

Hello,

So a few weeks back I was watching a YouTube video on my rMBP when the screen froze, and a stuttering noise was coming from the machine. I had to hold down the power button to turn the machine off however when I restarted the system it ran fine. After initial research I found this to be a sign of the Hard Drive failing, I ran the Hardware test and no errors came up.

Jump to several hours ago, I was browsing the web while listening to music, yet again the screen froze however leaning in closer I found the music audio to be stuttering rather than a stuttering noise from inside.

This makes me think the first time it happened it was simply the audio stuttering and not something stuttering/clicking from inside.

Hopefully that all makes sense.

Has anyone else experienced this? I assume its software related (hopefully) and not hardware related.