Really nice additions and polish! I especially like the decision to open up the boundaries of the environment. It nicely acknowledges players who don't choose to stay on the main path and makes the space around you feel even more expansive and surreal.
The only thing that feels a bit off for me is the trigger behavior for the alien musicians. Partly because their animations suggest they are always playing I feel like their music should fade in and out as I get closer or farther away, rather than abruptly come in or cut off when I approach or walk away. I think they would feel more integrated into the space if either their music had a smooth distance-based roll-off or if their animations only played when you can hear them. Also, this might take more effort than its worth, but it would be a really nice touch if their animations exactly matched their music, only moving on each note.