Locrian: A Not-So-Scary Approach to the Leading Tone Mode (Part 2 of 2)
How to treat Locrian as a harmonic driving force instead of a sour set of notes.
Diminished TriTone Subs
A TriTone Substitution (which is commonly called a TriTone Sub) is where you take a Dominant Seventh chord's TriTone interval notes, swap their order, and rebuild a new Dominant Seventh chord based on those notes. We can do the same thing with a Half-Diminished chord as shown below.
This is not a common way to move to a Tonic as it places a m7b5 two and a half steps above a major chord and two whole steps below a minor chord. You can think of this as replacing the Lydian chord in your song with a Locrian chord. This may or may not make sense depending on your point of view, but let's give it a shot.
Lydian and Locrian are only one degree change apart from each other, but the degree to change is the first degree. This would take a mode like F Lydian and transform it into F# Locrian. The keys that these modes come from are only a fifth apart and are the keys C and G. We can go from F Lydian to F# Locrian and then arrive at G Mixolydian, but that would be a modulation. Modulations are a topic that I'll discuss separately. To stay focused on Locrian, I'll use F Locrian in the key of C.
Placing Locrian as our fourth-degree structure contradicts a lot of what we've covered so far because it places Locrian a half-step above a minor chord and a whole step below a major chord, which is the reverse of what we have between the chords Am7, Bm7b5, and CMaj7. What we can do is pair it with the TriTone Sub of Db7 which uses Mixolydian. By playing F Locrian in conjunction with Db Mixolydian we can lead down to C Ionian in a more natural way. Check out the audio clip that does just this and try it out for yourself.
Pairing with a Secondary Dominant and Secondary Diminished
We can take the Dominant functionality of Locrian yet another step further and combine it with Mixolydian in other ways to lead us to a variety of major and minor structures.
By using the concepts we've learned so far, we can continue to blend Locrian with Mixolydian to move toward any major or minor. The most important thing to be aware of the tension that is created, and the context of the sound used. The best way to think of this is to try out a Secondary Dominant or Secondary Diminished chord to a major or minor chord as we've already done. Then blend in or completely substitute in the corresponding Mixolydian or Locrian mode. This means that any time you play a Mixolydian Secondary Dominant you can go up two whole steps from your root note to play Locrian. The same goes in reverse. A simple way to think of this is to take a Diminished Triad like B-D-F and add a new root note like G to create a G7 chord, G-B-D-F. We can also drop the note G and now our chord is diminished.
Double Flat That Seven
We've stuck to the Half-Diminished format since that is what Locrian gives us. The Half-Diminished structure is simply degrees 1, b3, b5, b7. We can manipulate this format and use a Fully Diminished (notated as ˚7) structure that uses degrees 1, b3, b5, bb7 (called double-flat seven). The bb7 uses the same note as the sixth degree, but because the bb7 takes the place of the sixth degree it is implied that we now have a degree b6 to use.
This is just like what happens when the degree between the 4th and 5th degree is used. If we use a #4, then we cannot have a b5 and therefore a 5th degree is used. If we have a b5, then we cannot use the #4 and a 4th degree is used. In a Fully Diminished structure we have a bb7, so a b6 is implied.
The reason why I want to point out the bb7 along with Locrian is because we can use it as a substitute for Locrian. Harmonic Major's seventh mode is Locrian bb7. It functions the same as Locrian, but with some added features. A chord that is built from degrees 1, b3, b5, bb7 only uses minor third intervals, which is an interval of a step and a half. This symmetrical structure calls for resolve, which we can do by following a few simple rules.
Rule 1: Always resolve to a chord/structure with a perfect fifth. Rule 2: Always resolve to a chord/structure with a root that is NOT part of the °7 used. Rule 3: The chord/structure resolved towards will feel like a Major Tonic (typically Ionian) or a Minor Tonic (typically Aeolian).
Let's use B˚7, which gives us the notes B, D, F, Ab. We can resolve this with any major or minor chord that is rooted in A, Bb, C, Db, Eb, E, Gb, or G. That's a total of 16 major or minor chords. Since only the fifth degree is needed, we can use any type of suspension chord as well, so if we include all the sus2 and sus4 chords our list of options grows to 48 triad chords.
Now this may be overkill, but the point is that it creates options and helps to set the Tonic note where you like. An example progression of this in the keys of C and Eb would be as follows.
In this setup we end every fourth measure with a dominant functioning chord that leads to a Tonic. The B˚7 let's us move to CMaj7, Am, and Cm because their follow the three rules. I used Cm7, Bb7, Gm7 in the progression because it highlights the third rule by using C Aeolian from the key of Eb. Fully Diminished structures like B°7 allow us to move our Tonic note around in the key we are using and within other keys. Try using these rules and see where they lead you. This is one of those fun parts of music theory where you take some rules, and then see what you can bend with them.
Weaving Locrian into Whole Step Spaces
This whole time we've looked at Locrian and diminished structures as things that lead us much like the Leading Tone in the Major Scale. There is a way to use Locrian as a "Passing Tone" or "Auxiliary Tone" as well. A passing tone is where you use a note literally in passing, like F, F#, G. The F# is note part of C Ionian and would be played to connect F and G. An auxiliary note is where you play a note in passing only to return to the original note. So F, F#, F would treat F# as an auxiliary note.
Using C Ionian for our chords we have CMaj7, Dm7, Em7, FMaj7, G7, Am7, and Bm7b5 with Bm7b5 as our Locrian chord. Going to other modes in parallel lets us start with the same note, in this case the note C, but we get a different set of chords. A great way to access Locrian besides Bm7b5 is by going from C Ionian to C Lydian in parallel. The only note that is different is the F#, which is the root note for an F#m7b5. This chord also uses Locrian. By focusing on FMaj7, F#m7b5, and G7 we can use Locrian as a “passing” structure.
Playing FMaj7 with the Lydian mode sounds great. To access F# Locrian all we need to do is sharpen the first degree of F Lydian. All other notes remain the same. Doing so takes F Lydian (F, G, A, B, C, D, E) and changes it into F# Locrian (F#, G, A, B, C, D, E). From there we can return to our C Ionian chords and play G Mixolydian (G, A, B, C, D, E, F).
Just like in previous examples, playing a m7b5 and then a major chord a half-step up makes the major chord feel like it is Ionian, so by playing the note F in G7 we can use the F#m7b5 in passing between the FMaj7 and G7 chords.
Just like an auxiliary note, we can also use F#m7b5 as an auxiliary chord. Simply playing FMaj7, F#m7b5, and FMaj7 again let’s us sharpen the F Lydian first degree note as a tense accent from F to F#. We can then flatten that note from F# back to F and briefly touch on a Locrian sound that sits right next to our Lydian sound. Here’s an example of treating F# Locrian as a “passing” and “auxiliary” structure. I’ve also borrowed a minor 4-chord so the last few bars use F as the root note while the intervals above it continually flatten to create some sonic texture.
