I've really liked these lectures so far, but as a reformed Christian I think it's important to note that Luther's most important and heartfelt contribution to the church other than putting the Bible back in the hands of the congregation is reviving belief in the gospel that is not by works, but by faith alone. I'm sure a German "work ethic" would bare little importance to him compared to the work-less gospel of free salvation through the merits of Christ alone.
fair enough however I believe it is correct to say that Brahms was virtually an atheist and chose texts that elided dogma and reading a quotidian celebration of stoical orientation fits the man.