Of the many changes introduced with Xcode 4, one of the least talked about is its new template format. But while most of the existing 3.x templates were converted to the new format, somewhere during the rollout of OS X 10.7 (“Lion”) the Audio Unit templates got yanked. Fortunately, reverse-engineering the new format from existing templates isn’t all that difficult. And: once you have a grip on how the new format works, it’s a pretty straight shot to restoring the AU templates, updating them to compile with Lion and Mountain Lion, and maybe even making a few tweaky improvements while you’re at it.