Xjyuk

One particular jazz piano technique is to voice chords using quartal voicings. A quartal voicing is a chord built on fourths. For example, one might voice Cmin with the notes (in ascending order) F-B♭-E♭. Iconic examples of this technique can be found in Chick Corea's album Now He Sings, Now He Sobs.

Jazz pianists often use this technique to "go out." That is, they often use quartal voicings to depart from the written chords/harmonies. However, quartal voicings are ambiguous. For instance, the chord above (F-B♭-E♭) could also be a voicing for E♭Maj, E♭min, B♭sus, G7♯9, D♭Maj, D♭7, etc.

So, in these contexts, how are quartal voicings used to "go out" when improvising?

Typically you choose the quartal voicing after you have decided on what mode to improvise with. For example, if the chord is Cm, you are likely to choose the dorian mode. Then you have many choices for quartal voicings that are enharmonic to that mode. The example you've given, F-Bb-Eb, is widely used over Cm because it includes both the 3rd and the 7th, but there are many (seven) quartal voicings of this shape that come from C dorian:

• C-F-Bb




• D-G-C




• Eb-A-D




• F-Bb-Eb




• G-C-F




• A-D-G




• Bb-Eb-A

(You might note that these are exactly the same as the voicings you get in Eb lydian or F mixolydian, which are equivalent modes to C dorian. But since the chord symbol was Cm, we know the bass note is C, so strictly speaking we should refer to this mode as C dorian.)

Practice making the quartal "claw" with your left hand and moving up and down the dorian mode enharmonically in this manner. If you play around with these voicings, you will notice that some feel especially dissonant, others somewhat hollow. That variance is what makes quartal comping interesting. As you comp, you can create little countermelodies by choosing voicings that match (or contrast) with what you're doing in your right hand.

This approach is discussed in detail in Mark Levine, The Jazz Piano Book.

Your question is about what notes you can use in your right hand, but I hope my answer makes it clear that the right hand and left hand are actually following a similar thought process when you use this approach to improvising. First, you look at the chord and choose a suitable mode. Then, you combine left hand voicings and right hand melodies to your liking according to that mode.

As for "going out," this term usually refers to when we break from the expected mode and play notes that normally "don't work." Quartal voicings (especially those that consist of perfect fourths only) are useful when playing out because they have such a symmetrical, strong structure. They sound OK even if you choose a quartal voicing with an arbitrary relationship to the tonic.

For example, after playing in C dorian over a Cm chord for a while, you may choose to create tension by playing in C# dorian for a phrase and then resolving back down. Your left hand voicing could move in parallel from F-Bb-Eb to F#-B-E for a moment, with the right hand following suit by playing melodies from the C# dorian scale, then you would resolve back on a C dorian voicing. It takes a lot of practice to learn to do this tastefully, of course, but Chick Corea makes for an excellent reference.

There are a lot of ways to think about this, in part because quartal voicings are so ambiguous. It opens the door to many different scale and chord pairings.

Harmonize a Melody Note with a Quartal Voicing Outside the Key

This is something we can hear Chick Corea doing. Imagine we're improvising over a Cmin chord and we want to play a lick ending on E♭. Instead of harmonizing the E♭ with a traditional Cmin chord, we could play the quartal voicing D♭-G♭-B♮ in our left hand, along with the E♭ in our right hand. The left hand thus "goes out," but the entire voicing D♭-G♭-B♮-E♭ sounds good.

This is something valuable to practice. Pick a note at random (like E♭), and in the left hand, harmonize the note with different quartal voicings that sound good. (It's worth noting that quartal voicings can be inverted.) For example, some quartal voicings that I like under E♭ are:
- D♭-G♭-B♮(-E♭)
- C♮-F♮-B♭(-E♭)
- B♭-E♭-A♭(-E♭)
- G♭-B♮-E♮(-E♭)

Use Movement of the Quartal Chords to Go Out

Another way to go out is to let the left hand take the lead. That is, play a quartal voicing that fits in the designated key. Then move the quartal voicing up or down a half step, a minor third, or any other interval which introduces notes that are outside the designated key.

Once you have your quartal voicing, pick a scale that works with it. An easy way to do this is to build a pentatonic scale from any one of the three notes in the quartal chord. For the voicing F-B♭-E♭, the "best fitting" pentatonic scales are F minor pentatonic, B♭ minor pentatonic, and E♭ Major pentatonic.

Or instead of using a pentatonic scale, another quick trick is to use a triad pair.¹ Build the triad pair from the top note of the quartal voicing (E♭Maj triad) and a whole step down (D♭Maj triad). So over the quartal voicing F-B♭-E♭, we could use the triads E♭Maj and D♭Maj. This is another great way to practice--pick a quartal voicing at random, and then improvise using the associated triad pairs.

Go Out the Traditional Way

Another more traditional approach is to simply pick a new scale that deviates from the given scale. For example, if you're playing over a Cmin chord, you could start playing in D♭min and then pull quartal voicings from the D♭min scale. Using this technique, common intervals to use are a half step, a minor third, and a tritone. So if you're improvising over a Cmin chord, you might switch to Bmin or D♭min, Amin or E♭min, or G♭min.

^{1. Generally, this technique involves building a six-note scale from two triads. Soloing built from this technique often use arpeggios that alternate between the two triads. There are good videos on YouTube about this technique.}