I've been going through a 1920's blues phase the past few months. I especially like the female blues singers from that time period: Bessie Smith, Clara Smith (no relation), Lucille Bogan (if you search her stuff on Youtube, be forewarned: it's really dirty), and Sippie Wallace. I have to laugh at how they got away with many of the lyrics! It was dirty, but more subtle back then.
Before that, I listened to 60's soul music. I love Sam Cooke's voice.
I also enjoy modern renditions of Civil War era music, a holdover from my reenacting days. Those cds got me through driving for 7-9 hours straight, exhausted from no sleep for 3 days! They may have literally saved my life on some occasions, like the infamous from Ft. Pickett, through the DC Beltway, to PA trip. Singing kept me alert and awake on many a nasty stretch of highway.