Washington, D.C. is associated with a great many things…but R&B?  Leave it to German label Bear Family to take the emphasis off politics to uncover a lost chapter of the American capital’s rich story.  R&B in D.C. 1940-1960 is the name of the upcoming LP-size, 16-CD box set comprehensively surveying two decades of regional music as only Bear Family can – with 472 tracks (that’s around 20 hours of music) and a 352-page hardcover book.  This one-of-a-kind set is due on September 3 and limited to just 1,500 copies worldwide.  It spotlights…