Many are deejays—professional or only-in-their-minds. Whatever their status, they are the most dedicated crate diggers, content to spend hours laboriously going through boxes of 7 inch 45s, looking for their holy grail. Although garage rock fans are obsessed, it's the R&B fanatics who become most consumed. Finding that elusive, unknown, super cool jam that no one else has, drives them into basements, thrift stores and swap meets.
The market for rhythm & blues,…