An update: I think this guy may just be bad a communicating in general. Some other musicians and I were exchanging e-mails about a concert and rehearsal over the course of multiple days and no one heard anything from him. I had to keep reminding him to reply to another e-mail about another rehearsal. But I didn't text him this time because guess what, I'm not his mom!

At least it means that it might not be me, he just can't communicate efficiently.