I am learning a slow blues called After hours in a video lesson with Johnnie Johnsson. It includes some sheet music with this chord progression: 1:G 2:C7 3:G 4:G Db9 5:C9 6:C9 7:G7 8:G7 9:G/A 10:D G/D D 11:G C 12:G/F Eb9 D9 Ab9 G13 13: G13

This very different from the normal 12 bar progression I'm used to when jamming. The Db9 chord is not even included in the key of G. How do we explain this chord? There are a lot of chords in bar 12. Is this a standard slow blues turnaround? There is also a 13th bar but I guess that just included as an ending. Is this the standard ending that I often hear in blues? Ending on bar 13?

Is this chord progression a standard progression that one should remember if there is an interest in slow blues? If I'm correct one could just write all the chords without the numbers which would make G13 just a G chord in the sheet music? Its is my understanding that this often occurs in leadsheets.

  • Note that you can approach any chord in a blues progression (and elsewhere) by the same type of chord a half step above, so e.g. approach C7 by Db7, G7 by Ab7, etc. This will explain a lot in your progression. Try to hear and understand which chords are fundamental to the progression and which are just approach chords and embellishment. – Matt L. Nov 29 '15 at 10:23
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    The Db9 is a flat 5 substitute for a G7 which would resolve to the C9. this creates a chromatic resolution to C9. – ggcg Jul 5 '18 at 0:28

It's not far off the standard 12 bar blue format. The first four bars are commonplace, but with a tritone substitution with a Db9 to lead to C9.Next four bars, standard again, then an altered turnaround, using chromatics, Eb9 to D9 and Ab9 to G something. Turnarounds are the most adulterated part of 12 bars, with many, many different ideas being used. I guess the G13 is a pushed chord to get to bar 13, which as you state, is probably bar 1 again. A 13th chord is rare as an end chord, but as an adapted 7th/9th, it fits with the blues idiom. Again, I'm guessing it's in 12/8 time, so changes aren't too rapid.

Yes, all chords can be written - and played - as bog-standard majors, but then, the blues feel would be lost somewhat.

It's not worth remembering per se. Often, a player will put these embellishments into a piece, just to spice it up, or relieve the tedium of an ordinary 12 bar sequence. Look at Stormy Monday, another example of an original 12 bar, changed very nicely with several chords that are unexpected, but add a heck of a lot to the accompaniment.


Db9 is not DIATONIC in the key of G (neither is G7 come to that!). But it's very often INCLUDED in songs in the key of G. Do you know about the 'b5 substitution'? It exploits the fact that the tritone is symmetrical, it's still a tritone when inverted. The tension notes in G7 (F and B) also occur in Db7 (as F and Cb). Any chord containing those two notes is going to be able to act as a dominant 7th leading to C. Or, for a less 'theory' way of looking at it, just know that as well as getting to C from G7, a 5th above, you can effectively slip down from the chord a semitone above.


I'd have a couple questions about this progression for you. First, is the 13th measure just going back to one, or is it really a 13 bar progression? Rewriting it with bars helps. Second, does the 12th bar really have 5 chords, or is there a typo?

| G | C7 | G | G Db9 | C9 | C9 | G7 | G7 | G/A | D G/D D | G C |

G/F Eb9 D9 Ab9 G13 | G13 |

First off, not all blues progressions are 12 bar blues. There are 8 bar progressions and multiples of 8 and 12.

Second, there is a basic (very simple) template for the 12 bar blues that is greatly embellished by jazz and blues artists. Sometimes it is so embellished it is hard to find the patterns other than counting 12 bars. In it simplest form one has (in G):

| G | G | G | G | C | C | G | G | D | C | G | D |

The "land marks" for lack of a better term are indicated below (this is somewhat subjective).

| G | - | - | - | C | - | G | - | - | - | - | D |

Staring on any chord we expect a jump to the IV at measure 5, and back to I in measure 7. After that there has to be a "turn around" in the last measure that "USUALLY" ends on the V (V7) to resolve back to I. Dominant 7th chords (or an extension) are almost always used for each chord. Most players expect a jump to V at measure 9 but this is not a hard and fast rule. In the dashed measures people often throw in cycle extensions and substitutions to the point of no return. But if you understand these cycles you can decipher the basic pattern and see the logic. Some players put Rhythm Changes in after the I in measure 7. One of the more common embellishments is to jump to the IV i measure 2 (called a fast 4), which yours has. Wes Montgomery jumps to the flat 7 in measure 2 in West Coast Blues. The Db9 is really just a substitute for the G7. I can't explain the 13th bar, but I once wrote a blues tune with 11 bars to create a particular feeling. The bunch of chords in the measure before looks like a turn around with substitutions. You might want to check out the following tunes. imo these are really 12 bar blues in disguise, some more disguised than others.

Stormy Monday

West Coast Blues

Blues for Alice

Good Bye Pork Pie Hat

Again, some of the changes are really stretching the template but it's in there. Chord substitutions and cycle extensions are a big part of the formula. But the blues has such a distinct feeling that you could stay on the G blues scale over the changes and develop a good solo (at least for starters).

  • How many tunes did you mention in your answer? 4 of them like I suspect (Stormy Monday, West Coast Blues, Blues for Alice, Good Bye Pork Pie Hat)? Having no commas or other separators really hurts that section. – Dekkadeci Jul 5 '18 at 8:54

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