There are two versions of the audio, one at a tempo ridiculoso of 200 bpm, and one at a human tempo of 120 bpm.
Same drill as before, these are mp3s that play 5 times through the progression (so 60 measures total), but they are loopable so if you play them in any app that allows looping (and is any good at it) it will keep going and going.
I use Quicktime player, it works great, its free, and it's already on your machine if you have a Mac.
Blues at 120 bpm
Blues at 200 bpm
There are some extra juicy chords in this progression, some might look a little strange if you are used to playing the standard 3-chord I-IV-V blues. There are a bunch of extra dominant chords for the turnaround, a couple diminished chords sprinkled here and there, and even a fancy little thing called a tri-tone sub.
This tri-tone sub character shows up in measure 4, it is that E7, right after the Bb7 and right before the Eb7.
Here is the idea behind this crazy thing - the most important notes (other than the root) of any chord are the third and the seventh, because those are the notes that give away what type of chord it is, either major, minor, dominant, whatever. So those notes matter the most and the rest are somewhat secondary. There are a lot of piano players that don't even play the root sometimes, they just leave it out.
Now for the wild part: these two different chords, the Bb7 and the E7 have exactly the same third and seventh, they are just switched!. So that means if one were sneaky one could actually use one in place of the other if one wanted to make things sound a little more interesting. Check it out.
If we were going to follow the "rules" we would put a Bb (and lets just go ahead and make it a dominant since this is a blues shall we?) in front of the Eb, so we would get Bb7 to Eb7, or V to I. And that is how measure 4 starts, with a Bb7. So far so good. But then comes this E7. Huh?
Since you are a chord spelling master, you can peer into this mystery to see what notes make up both of these two chords in measure 4, the Bb7 and the E7.
Notice anything? The important notes, the third and the seventh of both chords are THE SAME, just inverted. No way. Ya-huh. The third of one is the seventh of the other and vice versa. Oh, they try and deny it by going all enharmonic, but Ab is the same thing as G# remember, so when we pierce their little web of lies what we have is:
This is a tri-tone sub, you take a chord a tri-tone away from the chord you want to substitute for because it has the same juicy important notes (third and seventh) as the original chord. E is a tri-tone, or a flatted fifth away from Bb, but they both have a G# (or an Ab) and a D in them so they can behave very very similarly, and if you want, you can use one in place of another.
- Bb - root
- D - third
- F - fifth
- Ab (G#!) - seventh
- E - root
- G#(Ab!) - third
- B - fifth
- D - seventh
Now instead of a measure of a single Bb7 chord, this progression does some ridiculoso extendo by adding that E7 after that Bb7 and now there are two different (but the same!) chords per measure and some additional choices are available for soloing instead of just have one chord per measure as a garden variety I-IV-V blues usually has.
So there ya go. The Tritone Substitution. This doesn't necessarily make the progression "better" or anything, it is just another way to add some interest to a blues.