How to Add an "Archive" Keyboard Shortcut to Mac OS X Mail

Surely, Boismortier gets five stars. Five stars also for Buxtehude. Pickeringe? Five stars!
Surely, better ways exist to rate music in iTunes as a keyboardist. Not in iTunes itself but in "System Preferences", you can set up harmonies on your clavicytherium to award stars.
In very like a manner, you can add a combination for awarding archival status to emails in Mac OS X Mail:
›› Like the "Archive" button in Mac OS X Mail but wish there was a keyboard shortcut? Here's how to set up a key combination for archiving in Mac OS X Mail.