the online magazine for bass players

Search Menu

Understanding Blues Forms and Common Substitutions

In this lesson, we’re going to examine a couple of different blues forms, specifically the 12 bar, 8 bar, and 16 bar blues. Additionally, we’ll go over a few different approaches to playing through the form and knowing when it would be appropriate to substitute chords or when to adhere to the traditional changes.

Here is a diagram outlining the standard 12 bar form:

12 Bar Blues

The roman numerals I, IV, and V refer to the “one,” “four,” and “five,” chords in the progression. If you’re new to music theory, think of playing a C major scale and attributing a number to each note of the scale. C=I, D=ii, E=iii, F=IV, G=V, A=vi, B=vii (lower case indicates minor chord). If we’re playing a blues in the key of C, the I chord is C, the IV chord is F, and the V chord is G.

Some common substitutions in the form include a “quick IV,” where the second bar of I is changed to a bar of IV. Another common change is a “ii-V turnaround” which applies to bars 9 and 10. If we were in the key of C, the changes would go D to G instead of G to F.

16 bar blues progressions are similar to the 12 bar blues, however the one chord is held for 8 bars instead of 4 at the beginning of the progression. Many blues songs have verses that follow the 16 bar form and then switch to a 12 bar form for the chorus or solo sections.

16 Bar Blues

An 8 bar blues typically follows this pattern:

8 Bar Blues

Think of the song “Key to the Highway” to hear this progression. A common alteration for this progression is substituting a VI chord (A in the key of C) for the IV chord in the third bar of the progression.

Now that we’ve gone over the basic forms for these chord progressions, it’s time to think about how we can approach playing through these changes. Think about who you’re playing with and whether or not the players intend to play traditional blues or jazzier blues.

The traditional blues players typically want the bass player to stay true to the form. It’s the bass player’s job to clearly outline the I, IV, and V chords and to stay with a specific bass pattern. There isn’t much room for improvisation when it comes to the chord changes because the lead instrumentalists or vocalists are expecting to hear the standard 12 bar changes; therefore, if you find yourself playing in this situation, chord substitutions usually are not welcome. Some blues standards dohave other kinds of turnarounds, such as “The Thrill Is Gone” where the turnaround is ♭VI-V-I instead of V-IV-I, so it’s best to familiarize yourself with some standard tunes.

One common complaint that I hear is that bass players find it “boring” to only play over these three chords. If you find yourself getting bored, think about howyou’re playing the notes. Appreciate how a simple part can be exactly the right thing and that the other members of the band want your bass line to sound a certain way.

Many jazz players will say “let’s just jam a 12 bar blues” or they may suggest jazz standards that follow a 12 bar form (such as “All Blues” or “Blue Monk”). In this situation, you may be able to take some liberties with the chord changes by using substitutions or passing tones. With blues players, the turnaround is implied to be V-IV-I, however, my experience playing with jazzier ensembles suggests that ii-V-I is the preferred turnaround.

The best thing to do any playing situation is to listen. By paying attention to the other players, you’ll hear the chord progression that they play as well as the chord substitutions that they use. Make eye contact with the keyboard player or rhythm guitarist to see what they are doing. They will appreciate your willingness to follow along with chord substitutions and it will help you develop your ear. Be on the lookout for common changes, such as a chromatic move from the I to the VI chord (followed by a ii-V-I turnaround) or for an extended circle of fourths change: vii-iii-VI-ii-V-I.

Although there is no guaranteed way to know exactly what to play every time you get on the bandstand, remember that your ear is the best tool you have. Also, keep context in mind and feel out the other players. If you’re playing a blues gig, remember to stick to the chord progression and focus on groove. If you’re playing with jazz players who call a 12-bar, be on the lookout for other changes in the progression. The more you play with someone, the more you’ll hear certain tendencies in their playing and if you’re familiar with various blues forms, substitutions, and standard progressions, the more prepared you’ll be.