These are some of the shows I noticed on WTVS Detroit and WGBH Boston for September:

WTVS

Sept 5th
4:00am Why the Cowboy Sings    1 Hour

Sept 6th
11:30pm American Masters "Muddy Waters: Can't Be Satisfied"    1 Hour

Sept 7th
2:30am Austin City Limits "Nickel Creek/Ralph Stanley"    1 Hour

Sept 14th
12:30am Soundstage "John Hiatt; Dar Williams; Robinella and the CCstringband"    1 Hour

Sept 21st
midnight American Masters "Muddy Waters: Can't Be Satisfied"    1 Hour

Sept 28th
3:30pm American Masters "Muddy Waters: Can't Be Satisfied"   1 Hour

WGBH

Sept 13th
midnight Austin City Limits "Bonnie Raitt With Special Guests"

Sept 27th
9:30pm Legends of New Orleans: The Music of Fats Domino

Sept 28th
midnight Austin City Limits "Alison Krauss & Union Station/The Flatlanders"