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We've all surely played 12 bar blues songs, with/out turnarounds, etc. Question is, although there are many, many variations on that basic 12 bar sequence, what actually needs to be there to retain its status as a 12 bar blues. Merely having 12 bars isn't enough.

  • Tension, Resolution and Exaggeration of passing notes in chord phrasing (d7’s and 9’s etc..) – jazzboy Nov 11 '17 at 13:02
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    @jazzboy - a lot of music needs these aspects. – Tim Nov 11 '17 at 13:33
  • The canonical 12 bar blues is fairly recent and there are still plenty of popular 8 bar blues tunes. In some more exotic or older forms you'll also find 9 bars, 13 bars, etc, 'boogies' with no form at all... Buddy Guy's Sweet Tea explored some of this material. IMO this question is a very narrow, academic exercise, and has little or no practical implications. – Stinkfoot Nov 12 '17 at 1:54
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    @Stinkfoot - the 12 bar blues is so ubiquitous that I chose to highlight that particularly. Yes, there are blues in other forms, but the 12 bar is so common, it's what just about every guitarist has played and recognises as the blues, even though other forms exist. The question is purely concerned with this form, and I feel that certain points in the sequence need to be there for a player to say 'yes, it's a 12 bar blues'. But a consensus on that is still awaited. – Tim Nov 13 '17 at 7:00
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    @Stinkfoot, if I ask a question on this site about Mozart, that doesn't mean I hate Chopin because I didn't ask about Chopin. I just might happen to have a specific question about Mozart. Tim is asking a specific question about the 12-bar blues. It's not the only blues form that exist. What do those other blues forms have to do with this question? He never said "12-bar blues are the best" or "12-bar blues are the true blues form." He's asking what defines a 12-bar blues. What's the disagreement? I agree that there are mainstream 8 bar tunes, but I don't see what they have to do with this Q. – jdjazz Nov 14 '17 at 5:05
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Essential Structure

I think this is a much harder question to answer than it might initially sound. In my mind, these are the most fundamental features of a 12-bar blues:

enter image description here

We start with a I chord in bar 1 and move to a IV7 in bar 5. We resolve back to the tonic in bar 7. Then we move to a V7 chord in bar 9, which resolves back to the I chord before the form repeats. That's the essential structure. While we can add a lot of additional things to the structure, we can only make very small changes (if any) to it.

In most cases, through the form the I chord is actually a I7 chord. Variations are possible though. For example, Blues For Alice uses a IMaj7 chord. So in the picture above, it's left as a I Chord, which could become IMaj7 or I7.

Bar 7

In bar 7, the crucial sound of a blues is resolution to the tonic. But while this is almost always done with a I chord in bar 7, it could be achieved with a iiiø7 chord in bar 7 instead. For example, using CMaj as the tonic, bars 7-10 could be:

enter image description here

The iiiø7 chord provides similar resolution to the tonic (Eø7 is equivalent to C7/E), but it also leads into a ii-V7 in bars 9-10.

Bars 9-10

In essence, there are two main choices for bars 9-10. The classic blues sound uses a V7-IV7 progression. The classic jazz/bebop sound uses a ii-V7 progression. For example, in Cmaj:

enter image description here

So the V7 chord can be delayed from bar 9 to bar 10, and when this happens, a ii chord is used in bar 9.

Bars 11-12

In bars 11-12, there are many turnarounds available, but none are needed. The blues can simply conclude with two bars of I7. But it can also lead back into the top of the form using one of these classic turnarounds:

  • iii-VI7-ii-V7
  • I-VI7-ii-V7
  • I7-I7-V7-V7

Moreover, virtually any chord in the turnaround can be replaced using a tritone substitutions, which further expands the options for bars 11-12. For example, in CMaj, a few options might include:

  • | CMaj | E♭Maj | A♭Maj | D♭Maj |
  • | C7 | E♭7 | Dmin | D♭7 |
  • | C7 | A7 | A♭7 | G7 |

Additions

The sections above outline alternative versions that slightly change/modify the essential form I've described. But this core structure merely provides the bones/framework, and there are many additions we can be make to fill in the empty bars.

In bars 2-4, it's common to add other chords (though this isn't required to qualify as a blues). Using CMaj, some of these additions might include:

  • | CMaj | F7 | C7 | C7 |
  • | CMaj | F7 | C7 | Gmin C7 |
  • | CMaj | Bø7 E7♭9 | Amin D7 | Gmin C7 | (Bird blues)
  • | CMaj E♭7 | A♭Maj B7 | EMaj G7 | CMaj C7 | (Coltrane changes)

In bars 5-8, still using C as the tonal center, a couple additional chords could include:

  • | F7 | F♯o | C7 | A7alt |
  • | F7 | Fmin B♭7 | Emin A7 | E♭min A♭7 |

This list of additions is definitely not comprehensive, and is probably biased toward jazz, which is what I'm more familiar with. It's nice to show, though, because in all of these iterations, we can still see the essential structure from above preserved.

  • Pretty comprehensive! Thanks. Bar 2 often gets a change, too, to IV, or IV and Io. So, the essence so far seems to be start on I (no surprise there!), bar 5 needs to be IV, and 9/10 will be possibly V/V to V or V to IV? Turnaround on 12 optional. – Tim Nov 11 '17 at 14:27
  • Yes! Agreed. I also forgot to mention that the I chord can be a I7 chord (as is most common) or a IMaj chord (a la Blues for Alice). – jdjazz Nov 11 '17 at 14:37
  • And also as a I9th. Bar 4 as I#5 or I7#5 isn't unusual, too, getting to IV (bar 5). And, lest we forget, I features in minor blues, which often has bar 9 as III. I'm looking for, I suppose, the quintessential parts of 12 bar blues. – Tim Nov 11 '17 at 15:12
  • @Tim, I assumed you meant a major blues rather than a minor blues. I think major blues and minor blues qualify as two distinct forms with very different substitutions, etc. I completely agree on the alterations you've mentioned. I didn't list any of the possible alterations because the options are so endless. For example, any single VI 7 chord alone could be replaced with VI 7 (b9), VI 7 (#9), VI 7 (b5), VI 7 (b9 b13), VI 7 (b5 b9), etc. – jdjazz Nov 11 '17 at 15:19
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    @Stinkfoot, there's no claim in this thread/question that a blues = 12-bars, with no exceptions. This is a question about the 12-bar blues. That might seem narrow in light of the other blues structures that exist, but then again the 12-bar blues is one of the most prevalent musical structures ever to exist. This doesn't mean other blues structures aren't relevant or important. They're just not the topic of this question. The ubiquity of the 12-bar blues points to something about the structure which is interesting to discuss. I think this question is worth thinking and talking about. – jdjazz Nov 14 '17 at 4:58
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There's a classic '12 bar blues' chord sequence with just I7, IV7 and V7. Beyond that, take it where you will (and many musicians have!) You want opinion? Ok, here's mine. If it starts on I7, moves to IV7 and ends back on I7, it's 12 bars long and it has a 'blues feel', I'll let it be a '12 bar blues'. That's enough 'points of recognition' for me.

There's a lot of Blues in 'God Bless The Child'. Who's counting?

  • If it starts on I7, moves to IV7 and ends back on I7, it's 12 bars long... Is IV7 mandatory? Wouldn't V7 also be sufficient? – Stinkfoot Nov 11 '17 at 22:45
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    That's a reasonable opinion. I personally feel discarding the IV7 takes it out of the category '12 bar blues'. How would you feel about staying on I7 throughout? Staying on I7 and not using any 'blue' notes? How many generations of giraffe can you breed into an elephant and it's still an elephant? – Laurence Payne Nov 12 '17 at 17:28
  • Staying on I7... | Boogie Chillun - John lee hooker - But no, not 12 bars... – Stinkfoot Nov 13 '17 at 2:22
  • You ask if I want opinion. Here, opinion isn't particularly accepted. I'm asking for fact. One cannot say 'it's 12 bars long. So it must be a 12 bar blues'. I'm asking, as in the question - what parts really do make up a 12 bar blues? We've had a lot of Stinkfoot's opinions - but not much guidance (until an answer). Or perhaps there just isn't a definitive shape or form, other than it's 12 bars long. In which case, Mozart probably wrote some... Other lengths of '12 bar blues' don't need to raise their heads! – Tim Sep 5 at 9:47
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what actually needs to be there to retain its status as a 12 bar blues?

It should be a 12 bar tune whose fundamental harmonic movement is represented by
I7->IV7->V7->I7, or any chords (or combination thereof) that are substituted^ for IV7 and V7 to produce functionally similar Tonic/Subdominant/Dominant/Tonic movement.

To be called a Blues, it should also use one of the traditional blues style rhythms, such as: Shuffle, Swing, Jump, Boogie, Walking Line, etc, or at least a hybrid rhythmic form comprised principally of such elements.


It should be noted that over the century or so that the genre has taken on an identifiable form, the term Blues has become much more narrow. In the 1920's, for example, any sort of rag, swing or stride tune or ballad that featured dominants could be called a Blues.

Here's a list of tracks from recordings of King Oliver's Creole Jazz Band, produced in the 1920s. Note the numerous titles featuring the term Blues, most (if not all) of which we today would not identify as blues at all - 12 bar or otherwise. enter image description here

Here's Mandy Lee Blues from that collection:

And here's Sobbin' Blues:


Several theory books I've read claim that the defining characteristic of all blues music is the use of dominants even in the tonic chord, unlike traditional western forms.


^ See: What are some chord substitutions for a I-IV-V blues progression?
and @jdJazz 's excellent answer here:
Chord sequences for 12 bar blues

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    These examples add a lot, and this is the only answer so far to mention rhythmic considerations, which are really important! +1 – jdjazz Nov 15 '17 at 2:07
  • Thank you for the in depth answer. All fine except I disagree that the feel must be as you say. There are plenty of blues - 12 bars long - which are straight 8, or four on the floor, don't swing, but still recognisable as 12 bar blues numbers. Nevertheless, +1. – Tim Sep 5 at 9:50
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Purely based on "it just don't feel right without it"...

It must have

I, I, I, I IV, IV, I, I, V, IV, I, I

at absolute minimum, not even 7ths required, root & 5ths will adequately state it.

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    Do you mean that's a good start point, or it must have that sequence - the most basic, most used version. I'm asking what and how much can be changed from that, and it will still be acceptable as a 12 bar blues sequence. I feel that maybe dom 7ths are needed to give it 'blues'. – Tim Nov 11 '17 at 12:10
  • Ah, then I misread your intent. My answer is, in effect, what's the absolute minimum it can contain & still be instantly recognisable as a "12-bar blues", not how far you can move away from that. – Tetsujin Nov 11 '17 at 12:13
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    I don't think the IV in bar 9 is necessary. In jazz, the V-IV-I is replaced with a iii-VI-ii-V. – jdjazz Nov 11 '17 at 13:04
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    But it is the 12 bar blues not 12 bar jazz – jazzboy Nov 11 '17 at 13:07
  • @jdjazz - you needn't venture into jazz. There are plenty straight blues tunes that dispense with that last IV, usually just holding on the V. – Stinkfoot Nov 12 '17 at 1:45

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