The barley made the rye a little darker than it would have been otherwise, and added an interesting flavor as well, complementing the rye nicely. I left this one seedless, but feel free to add caraway if you like.
If leaving a dairy product unrefrigerated overnight makes you nervous, you can refrigerate the mixture instead of leaving it on the counter. Let it come to room temperature the next day before you continue. Or use water instead of buttermilk.
This bread wasn't a fast riser, and the oven spring wasn't huge, either. But it's got a nice texture and good flavor. It would stand up nicely to big flavors - sauerkraut and sausages come to mind, but it's not so strong that you couldn't make a sandwich with it.