kdharris,

You might try The Land Where the Blues Began by Alan Lomax. He spends some time talking about Spirituals and their evolution.

You might want to look at some of his Southern Journey Series. If you go to places like CDNow and Amazon.com you will get some "clips" from the CD's.

Vol. 4 Brethren We Meet Again
Vol, 5 61 Highway Mississippi (Blues & Spirituals)
Vol. 6 Sheep, Sheep, Doncha Know the Road?
Vol. 9 Harp of a Thousand Strings
Vol. 10 Glory Shone Around
Vol. 11 Honor the Lamb

The Smithsonian had a recent touring exhibition called Wade in the Water, a history of African-American spirituals. Recordings at available at their web site. There are many clips available here.

For information about the traveling exhibition click here.

Good luck!

Roger in Baltimore