This lesson was designed for a jazz band class comprised of grade 9 to 11 students.

In order to be successful at improvising, young musicians have to become absolutely familiar with song structures. One of the most effective ways to do that is by learning to construct and play bass lines over different chord progressions. The bass’s function is to outline the harmony and form of a piece, and because the bass is almost always playing, locking in can help situate you and keep your improvising musical. If you lose your sense of the form, listen for the bass line and that will put you back on track.

A basic twelve-bar blues form hinges on three basic chords, one built on the first note of the major scale (tonic), one built on the fourth note (subdominant), and one built on the fifth (dominant). An F blues would look like this:

It’s important to have those scale degrees in your ear, and not only in your eye. Sing the first four scale degrees to take you up to the subdominant—“Here Comes the Bride” gives you the 1-4 interval. Sing from the first scale degree up to the fifth to get the feel of the dominant—“Twinkle Twinkle Little Star” is a quick memory trigger for 1-5. Practice finding those three pitches—1, 4, 5—then sing them through the blues form according to the diagram. Replace numbers with note names, and move it through a few keys, say C, F, and B♭. Practice until you can sing pitches by name effortlessly.

To construct a bass line over the blues, you use the mixolydian scale built on each of those three degrees. A mixolydian scale is only one note away from a major scale—the 7th degree of the scale is lowered one semitone, and that “flat seven” is one of the things that gives the blues its particular feel. For the F blues, you’ll build mixolydian scales on F, B♭, and C. Play through all three to get comfortable with the sound.

The mixolydian scale you use to build your bass line will depend on the chord in each bar over which you are constructing it. If a chord lasts for one bar, use the following pattern from the corresponding mixolydian scale: 1-2-3-5. If it lasts for two bars, use 1-2-3-5, 8-7-6-5. Here’s what that looks like:

Sing the pattern for each of the three chords, then sing the pattern through the blues progression. You’ve got a basic blues bass line!

One small adjustment will make your bass line smoother and more stylish. When you are descending toward measure 9, as you move to the fifth degree, slip in a semitone rather than playing the same note twice:

Commit your blues bass line to memory and practice until it feels completely familiar. At that point, the fun begins! Let various players in the band carry the bass line while others take turns improvising over it, then switch. Move through several keys, and learn new tunes or ‘heads’, that are built on the blues. You can also find a wealth of information by listening to the great soloists of jazz.

As you gain more familiarity with the blues form and more confidence in hearing how the bass outlines its structure, you will feel more comfortable when you solo, and your ideas will be more musical.