On Saturday, September 5, at 2 p.m., John Pizzarelli and Jessica Molasky (in her Tanglewood debut) will tape their popular radio program, “Radio Deluxe,” at the festival for later broadcast on more than 60 stations nationwide. Normally broadcast from their living room “high above Lexington Avenue,” the Tanglewood program will officially take “Radio Deluxe” on the road for the first time since the program’s inception in 2005. The show’s format, marked by the duo’s urbane, sophisticated humor, inventive playlist, and extensive knowledge of the Great American Songbook, is expanding its repertoire to include such rock-era voices as Randy Newman and Joni Mitchell.