Another important characteristic of a lot of blues is triplets: quarter notes divided into three equal parts intstead of two. For the slow rock blues think Fats Domino playing 12 to the bar, accenting 1,4,7,10: dahdahdahdahdahdahdahdahdahdahdahdah

or the quarter+eighth triplet: DAHdaDAHdaDAHdaDAHda

I have found lots of spirituals sound great with a bluesy treatment: "Just a Closer Walk with Thee," "Swing Low, Sweet Chariot," "Nearer My God to Thee," etc. Just accent the rhythms, use lots of sevenths, slide into long notes, walk the subdominant chord down to the second, go into the dominant seventh, then returning to the tonic, walk it down to a lower position. Add a harmonica to your arrangements, play it in second position (crossharp: C harmonica for G tunes) and bend and unbend notes, play the low growly two and three reed chords, use your hands for the wahs and the tremelos--dynamite.

Another blues progression I've been playing with a lot lately is that found in "Brown's Ferry Blues" and "Fare-thee, Titanic, Fare-thee-well":

/G.../G7.../C.../C7.../G.../G7.../D7.../....
/G.../G7.../C.../C7.../G.../D7.../G.../....

--seed

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