Update. Ash is becoming less and less shy in his cage. He used to kind of sit in his timberwood hideaway box in fear, I think, but he's rarely in it when I'm around. He will actually voluntarily climb into my palm to get out of his cage. If I lay down, he'll crawl all over me.
Last night, he got less time out his cage than usual and protested once he was put back in by sitting on top of his house and pouting. When I went to bed (a bit earlier than normal), it was the first night when he made a total racket. At one point, he made a loud series of noises
that sounded like this that I was kind of disturbed about - until I read about them this morning. Apparently, that's the noise a chinchilla makes when he wants to communicate that he is lonely or looking for his buddy.
I guess we're buddies now.