I’ve heard a lot of bass players who could play killin’ solos over a few types of chords and modes—flying high with pentatonic gnat-notes through an extended G7 vamp or bebopping over a basic turnaround in B
major. Most bass players first learn a few blues licks, then the major scale, then the Mixolydian mode, and then maybe a couple of all-purpose minor modes, like Dorian and Aeolian. But this field of slick licks and fancy footsteps tends to thin when harmonies become more complex. In my years of teaching and listening, I’ve found that many bass players skip or ignore one of the most common turnarounds: IIm75–V7#9.
Ex. 1a shows a Gm75 chord in two voicings. (The tablature shows how to get each chord’s characteristic notes on a 4-string bass.) Gm75 is sometimes notated G7 and called G “half-diminished” because it has the 5 but not the 7 of a “fully diminished” chord. The first voicing contains the chord’s basic notes: G, B, D, and F. The second voicing adds the 9th and 11th (A and C), upper chord tones that a pianist or guitarist might use to add additional color. You advanced players can think of this chord as a G diminished triad with an F major triad above it.
In major harmony, the minor 75 chord is built off the 7th scale degree, and its corresponding mode is Locrian. But in jazz it is more common—not to mention “hipper”—to play the Locrian 
2 scale over a m75 chord. Locrian 2 is the 6th mode of the melodic minor scale; in the case of Gm75 that would be B melodic minor. Why does it work better? Plain-old Locrian has a 2, which is an “avoid note” that clashes with the tonic of the corresponding chord. The Locrian 2, on the other hand, melds beautifully with the chord, particularly when another musician is playing the minor 75 chord with a natural 9th.
Ex. 2a shows two voicings of a C7 chord, which in a II–V progression is often “altered.” When a dominant 7 chord is altered, the 9th, 5th, or both have been raised or lowered by one half-step. The first voicing is C7#9#5, and the second is C795. There are many more dominant-chord alterations, but they all retain the same basic elements when used as the V7 chord in a II–V progression: a 3 and 7, the tritone interval which creates tension and which resolves smoothly to a I chord or another dominant chord.
Go to a keyboard and play the first voicing—you’ll notice that it’s basically a C7 chord with an A major inversion on top. Next play the second chord—it’s a C7 with a G major inversion. Slick, huh? Now you’re becoming one of the advanced players. Since altered dominant chords have so many variations, you’ll often see their chord symbol notated simply as 7#9 or 79, without specifying a #5 or 5. When keyboard and guitar players see these symbols, they often automatically add the 5 (also called the #4 or #11) or the #5 (also called the 13) to their voicing.
Ex. 2b shows the corresponding mode for an altered dominant chord, the diminished whole-tone or “altered” scale. The C altered scale is built from the 7th degree of D melodic minor. In addition to containing the essential “dominant” notes, the 3 and 7, it hits the colorful alterations.
Now check out Ex. 3 at “tempo di learn-o.” This etude is based on the harmony to Dizzy Gillespie’s bebop standard “Woody ’n’ You.” The A sections are in the key of D major, but the chord progression starts on Gm75 to C7#9, then moves around the cycle of 4ths with II–V clusters to the tonic chord, Dmaj7, in bars 7 and 8. In the first six bars, double-stops outline the 3rds and 7ths of the chords.
Bar 9 begins the melody over the Gm75. Take a close look and listen. In bar 10, the same melody moves up a minor 3rd to outline the sound of the C79. Do you remember that Locrian 2 is built from B melodic minor, and that the C diminished whole-tone mode is built from D melodic minor? The two melodic minor modes are a minor 3rd apart. That means you can play a lick built on the B melodic minor (G Locrian 2) that outlines the Gm75, and then move the lick up a minor 3rd to D melodic minor (C altered), which outlines the C79. When you have the melodic minor scale under your fingers, this becomes big fun—and a useful solo technique.
The etude’s B section moves through a series of II–V progressions (minor 7 instead of minor 75). This is a typical progression for bebop tunes with fast-moving chords—all you have to do is make the changes and hang on for the ride.
The last A section has the same chords as the first two A sections. On all of the minor 75 chords in this section, there is a melody built from the 1, 2, and 3 of Locrian 2. Note the use of both the 9 and #9 on the V7 chords in bars 26 and 30.
So now for a bit of straight-from-the-heart advice: You might be tempted to blow this whole etude off, because hey—it’s hard, it’s in D, the other guys usually solo on those tunes with minor 75 chords, and who needs to play in D anyway? Don’t do it—don’t just blow it off. You can master this—with careful, patient practice. I know, the theory gets a little involved, but hang in there. Trust me on this one: Once you really conquer melodic minor (and its nearby neighbors, Locrian 2 and diminished whole-tone), you can learn to let it rip on the IIm–V7 progression. And then you are well on your way to being one of “the advanced players.”