This is a classic Shandy Pants production, starting with a really interesting idea, leaning on some dry British humour, filling a world with weird blobby 3D, and built out enough to have some meat to it. I really liked the idea of playing a foley artist, trying to make the right noises to match up with a script. Despite the issues I ran into, I still had a ton of fun with this, although I did terribly in later levels and I think I got the bad ending.
Unfortunately, it also suffers from poor QoL, just like a classic Shandy Pants production. It has that awful feeling that something is going to break and you're going to have to restart from the beginning. There's a help screen, but I quickly forgot most of it and ended up trying to play through the whole game without using the time dilation thing. I'd love to replay levels, but I don't want to sit through unskippable cutscenes to do it (although there seems to be a nonfunctional "load game" button on the main menu). I found out after that I could have opened a menu to view help with ESC, I think, but I could have sworn I tried that to no avail.
It wasn't super clear how long I needed to have a sound playing for it to count, but maybe that was explained in the help, too. I wish the camera was further out, but I probably would have been able to get a better feel for the levels if I'd been able to use the portals and time dilation.
I think I've already implied this, but is definitely one of the most interesting uses of the modifier I've seen so far.