Watch the Adding the b7 online guitar lesson by Andrew Ford from Blues Bass Survival Guide
Another note we can add to the triad, 1, 3 and 5, and the major 6th in a blues bass line is the flat 7 or minor 7th. It is very prominent in boogie woogie or jump blues type lines as well as other styles of blues. Here are a few examples of how to use this b7 with the 1, 3, 5, and 6 to create a musical blues bass line. These first 4 examples have the 8th note rhythms interpreted as triplets.