Granny,
I learned as a child that sour milk is fine when used in anything cooked. Not only cake or bread or whatever, but even in sauces such as white sauce or gravy. Not clabbered, mind you, although I’d use those in biscuits in a heartbeat!
Yes, there are some recipes that beg for sour milk and I have always used it.....Corn bread is one of them.
We ate bowls of clabber, when I was a kid.
I like to use beer in pancakes and biscuits, when I don’t have buttermilk or sour milk, they are so light they will float, even when made with self rising flour or a common pancake mix.
Now I use the dehydrated buttermilk powder from Walton Feed.com in all the baking that I did, before I had to quit.
When I made cheese I also used the whey that remained in breads and gravies.
Forgive the short answers, as it is a weak arm day.