Sometimes when I'm squatting around maximal loads, I notice what could almost be described as a doppler shift in the music playing from my headphones for a brief moment. The music (maybe my perception of time?) seems to "slow down" slightly, or everything is processed more slowly. This happens during instants of extreme exertion.
This is a strange question, I know, but has anyone else experienced this? If so, what scientific explanation could there be for it? Any potential harm?
As noted above in the comments, there are two main reasons why this may be happening.
Adrenaline creates a perception of time dilation
Adrenaline can create a "bullet time" effect where time seems to move more slowly as your body routes blood to your brain. It's an evolutionary adaptation much like the fight-or-flight response to help you deal with a crisis situation.
Raised blood pressure results in perceived reduction of pitch and volume of hearing
As per Blurred vision during weightlifting, blood pressure increases during a lift, particularly if you're holding your breath, such as with the Valsalva maneuver. This can result in a dulled quality to sound in your hearing. Things sound more muffled and lower pitched. When a sound is slowed down, its pitch drops due to how frequency works, so when you hear the lower-pitched sound, there's a good chance you're interpreting it as being slowed down.
Lastly, while it's a remote possibility, maybe...
You're having your superpower origin
Watch a few movies involving superheros. A good bit of the time, as they suddenly discover their power, time slows down so that the audience can appreciate how momentous the situation is. If you start to hear triumphant background music coming from nowhere, or if one of your liftmates has started cackling evilly, there's a good chance you're the hero in the story. If so, watch out for glowing green rocks.
