Chris, he's right here and he's going to save you from having to try to relax when somebody's singing and wants you to actually concentrate on the words. I've listened to a lot of relaxing late night music after doing battle with the forces of evil, and any sort of singing is definitely out.
An "adagio" is a passage of slow music, typically peaceful and relaxing, and there are numerous recordings available under the search term "adagios". Here's
a nice collection, but I'd especially recommend this Debussy