Examples 1a and 1b show the ascending and descending chromatic scale in C, along with its intervals. Looking at the solfège (“do-re-mi”) syllables, you’ll notice that on the way up the scale, the shared intervals are given a name that identifies it with its diatonic relative. For example, scale degree 1 is called do, and #1 is di (pronounced “dee”). On the way down the scale, the same is true: 7 is ti (“tee”), and b7 is te (“tay”). In the real world, the solfège names of the chromatic intervals don’t come into play very often, but they are handy to know from a theoretical standpoint. Play through the chromatic scale, listening carefully to the sound of each note and its relationship with the tonic (C).

Ex. 2 shows the intervals from the chromatic scale that are not also diatonic to the major scale. Notice that these intervals come in pairs; the intervals in each pair sound the same, but they have different names. Because each interval can be referred to with either name depending on the application, it’s good to know that #4 is the same sound as b5, for instance. Work the chromatic intervals in Ex. 2; get used to the way they sound and how they lie on the fingerboard. Remember that there are always at least two ways to play each of them.

Now let’s simulate actual combat conditions: You’re filling in with a cover band, and they call a tune you don’t know. The song is a big crowd favorite, so they’re going to play it whether you know it or not. The guitarist gives you this info: “It’s a two-bar phrase in F, and it’s 1–4–b3–b6, all eighth-notes.” Ex. 3 is what you would wind up playing. Sounds like Teen Spirit to me! During the next set, the band calls another tune you don’t know—but no worries, because the keyboard player (named Ray) tells you: “Hey, man, it’s easy. It’s a two-bar phrase in A. It goes 1–b7–b6–5—play ’em as half-notes.” Ex. 4 is what you’ll play (or else they may tell you to hit the road, Jack).

This scenario happens all the time when you’re a subbing bassist, so it’s critical that you not only know the number system in relation to the major scale, but all of the chromatic scale’s “in-between notes” as well. When you have this information in your head and under your fingers, not only can you learn tunes on the job, you can transpose them to any key instantly without a lot of fumbling for the right note. Just for fun, play Examples 3 and 4 in the following keys: C, G, D, E, Bb, Eb, Ab, and any other keys that you like. You’ll find that when you connect the numbers to the shapes they create on the fingerboard, you can pick up new tunes very fast—and you can remember them, too.