What is the chord progression I hear at the end of a lot of blues songs?!

Usually in songs with a kind of 12/8 feel!. It sounds like the higher instruments are descending, and the lower instruments are ascending (although I'm more interested in the chords themselves than the specific instrumentation)!. It's got a slightly dissonant, moving-in-half-steps sound to it!. I hate to use onomatopoeia here, but the rhythm for the progression is something like:

dow
dut-dow
dut-dow
dut-dow now (sometimes holds out here)
dut-dow nowWww@Enter-QA@Com

---

---