Major and minor chords look like triangles on the lattice. They are closed loops, which I think contributes to their stable feeling. Up a major third, up a minor third, and down a fifth (due West on the lattice) brings you right back where you started. The intervals interlock, and they are all consonant, reinforcing the sense of harmonic rest.
Other combinations of notes are more open. Many chords look like straight lines on the lattice.
These chords often show up in my animations as fleeting transitional harmonies. In Flying Dream, for an instant, there’s even a stack of three major thirds:
To my ear, this stack of thirds has a distinctive sound, almost like cloth ripping.
A Suspended Second chord is a straight line, like an augmented chord, but on the horizontal axis. It’s a stack of two fifths. At the time the Sus2 and Sus4 chords were named, the 2 and 4 were usually “suspended,” or held over from the previous chord, as a tension to be resolved. Now they are often used as full chords.
The Police used these stacks of fifths a lot. Andy Summers’ guitar part for Every Breath You Take is full of Sus2 chords, alternating with major and minor thirds.
To me, Sus2 feels lightly stable, and wistful. All the intervals are overtonal, and quite consonant, but unlike the major and minor triads, the Sus2 doesn’t come full circle. If it keeps going, it will never return home, but climb on up the endless spiral of fifths.
It’s a great way to end a certain sort of song, finished but with a sense of longing.
The Suspended Fourth consists of a root, a perfect fifth, and a perfect fourth. The Sus4 looks the same on the lattice as the Sus2. The difference is the root.
This chord has a wonderful tension. The root establishes home. The 5 is overtonal, stable, with strong tonal gravity that attracts. The 4 is reciprocal, unstable, with a strong tonal gravity that repels.
Resolving to the 3 is satisfying indeed, as the unstable 4 slides from its unstable peak into the stable gravity well of the major third.
Sus4 chords are all over rock music. Pinball Wizard is a study, here it is by Townshend on acoustic guitar:
Chords and other collections of notes have consistent, recognizable shapes on the lattice. A major chord is a triangle sitting on its base, a minor chord is a triangle on its point. Yesterday’s post has videos showing these chords.
In the songs I know and write, the next most common chords after major and minor triads are seventh chords.
By convention, a “seventh chord” means a triad, with a minor seventh added. If the added seventh is a 7, or major seventh, it’s called a “major seventh” chord.
A minor seventh is an interval of ten half steps, or two shy of an octave. There are three different minor sevenths in the inner lattice, and each one makes chords with a different sound and function — that is, if you are playing in just intonation, or untempered. In equal temperament, the minor sevenths all sound the same, but there is still profit in knowing that they are different, because they function differently in chord progressions.
The 7b7, at 969 cents. This is 7/4, the harmonic, or barbershop seventh, a consonant note that appears in the actual harmonic series of the tonic.
Here are some movies in just intonation, so you can hear the differences.
————————————–
First, the b7, added to a minor chord.
A pretty sound, I like it! In equal temperament, this note is at 1000 cents, 18 cents flat of the b7, a clearly audible difference. Here’s the same movie in ET:
Both the b3 and b7 are decidedly flat. The b3 especially sounds different, a lot more dissonant and “beating.”
I wrote a post a while ago, exploring this minor seventh and how it sounds in an untempered chord progression. It’s here.
—————————————-
The next minor seventh is enormously important. This is the dominant-type seventh, b7-, 996 cents. It is fortunate that it is so close to the equal tempered note, 1000 cents, because that means its effect is barely diminished in ET — and it is a really important note in classical music.
The reason it’s called a dominant-type seventh is because it most often shows up with the dominant, or V chord. The note two steps south of the 5 is the 4 — and when you add a 4 to a V chord you get this:
The 4 is a powerful note in this context. It has strong tonal gravity, with reverse polarity. I’ve written several posts about this — here’s one about polarity, here’s one about the use of dominant seventh chords.
Here’s how the chord sounds when it’s built on the 1, in just intonation.
There is strong dissonance when that seventh comes in, and it’s dissonance with a purpose — the chord “wants” badly to resolve somewhere. In this case, it wants to resolve to the 4, the empty space in the middle of the chord. The 1, 3 and 5 are all in the harmonic series of the 4 — that is, they all appear in its “chord of nature,” the overtones that accompany a natural sound. So these notes sort of point to the 4. They point to the 1 even more strongly, though, until that b7- comes into the picture.
When you add the new note, the b7-, something new happens. This note points hard to the 4, and in a different way. It’s as though it says, “home is over there, go!”
The entire note collection “wants” to collapse to its center, like a gravitational collapse. The b7- helps to locate that center on the 4.
This effect is often used to move the ear to a IV chord. For example, if you want to start the bridge of a song on the IV, it helps to hit a I7 first. If you’re playing a song in G, and want to go to a C chord, a quick G7 will make the change seem more inevitable. Here’s that move in slo-mo.
The pull of the dominant-seventh-type chord is so strong that it is the sharpest tool in the kit for changing keys, or modulating. Classical composers use it for this constantly.
———————————
The last of the three is a beauty. This is the 7b7, the quintessential note of barbershop harmony, the harmonic seventh, 7/4. The b7- is highly dissonant, the b7 rather neutral, and the 7b7 highly consonant. It sounds (and looks) like this:
This is a resolved chord. In fact, if the consonance and stability of an interval are determined by the smallness of the numbers in its ratio, these are the four most consonant notes of all — 1/1, 3/1, 5/1 and 7/1.
Here is another opportunity to compare just intonation with equal temperament. The harmonic seventh and the dominant seventh sound exactly the same in ET. I believe that a good composer knows, consciously or not, which one is meant.
A good example is the “… and many more” ending so commonly added to Happy Birthday. It is clearly not a dominant type — it’s intended to mean the end of the song, even to put a stronger period on it than the major triad by itself. It’s a quote, or a parody of blues harmony. Play it on the piano and it will be tuned exactly like a I7 chord, but the ear can tell, by context, that there is no move expected, to the IV or anywhere, because it’s heard that little melody a thousand times, and it belongs at the end of a song.
But the signal is so much clearer when the tuning sends the message too! The 7b7 is at 969 cents, a third of a semitone flatter than the piano key.
By the way, I think this is why a common definition of “blue note” is “sung flatter than usual.” I believe the blue notes are the world of multiples of seven, and these just happen to be flatter than the closest notes in the worlds of 3 and 5, the basic lattice.
Here is a video of the 7b7 chord that starts with the harmonic seventh, goes to the equal-tempered seventh, and back to the 7b7.
Quite a difference. ET works because it implies the JI note, and the ear figures out what it’s supposed to be hearing. But the visceral impact is lessened a lot — in this case, IMO, completely.
Real Girl has several examples. The clearest is a guitar lick in the chorus:
That 7b5 is tasty over the bVI chord. For an instant, it makes a “barbershop seventh,” the 7th harmonic of the root.
Here is a vocal example from the same song:
The melody visits the blue tritone on the way up, and again on the way down. I especially like it on the word “like,” the blues flavor of the septimal note comes through loud and clear without it being strictly blues at all. For me, this fusion of septimal notes to the European collection is the great contribution American music has made to the world. I wrote an early article on this, with some examples, here.
These bits of melody that visit the 7b5 are very similar to the ones that incorporate the 7b3. The septimal flatted third is the melody note of major blues tonality. It functions as the seventh harmonic of the IV chord, just as the 7b5 is the 7th harmonic of the bVI chord. Here’s an example from Flying Dream:
Hear the similarity? Try going back and forth between this video and the guitar lick in the first video.
One of the beauties of the lattice is that the patterns repeat everywhere. If you move a pattern to a different part of the lattice, the new notes will have the same relationship to each other, but the musical context will change and it will convey a different feeling. This is a splendid compositional tool, and helps me greatly in understanding harmony.
I have a favorite note. Don’t tell the others. It’s the septimal flat five, or septimal tritone. I call it 7b5 on the lattice.
There are many reasons why I love this note. One is that Jimi played it, and he’s my favorite musician of them all. Another is that this note is rarely discussed in music theory (try googling it and you will find a few references), which allows me to sort of plant a flag in it. But the biggest reason is that the 7b5 opens up a whole world of melodic and harmonic possibility, and unlocks the minor blues.
The ratio of the septimal flat five is 7/5. It’s a tritone, a note smack in the middle of the octave, between the 4 and the 5. Tritones are famously dissonant. There are three of them in the inner lattice — the 7b5, the #4+, with a ratio of 45/32, and the b5-, whose ratio is 64/45. The 7/5 blue tritone is the most consonant one, by which I mean it has the smallest numbers in its ratio.
Most traditional blues are built on major chords, the I, IV and V, with septimal, or blue, notes in the melody. The 7b3 is especially important — there are entire songs that hang out forever on this note. These blues are major in character — everything happens above the central spine of the lattice.
The 7b5 is different. It lives in the minor part of the lattice, below the central spine, which allows for a whole different set of chordal harmonies. The 7b5 is a blue note that works with songs in minor keys.
Here are a couple of striking examples. First, I invite you to listen to a bit of Dizzy Miss Lizzy, by The Beatles. This is a major blues, played with I, IV and V chords.
George is exploring a delicious melodic zone that includes four major/blues melody notes in a tight group: the 2-, 2, 7b3, and 3, all in the span of two piano keys. As the I-IV-V progression rocks back and forth from left to right, between dominant and subdominant territory, the melody subtly shifts with it.
Listen again to the intro of the song. The riff repeats, but it’s not always tuned the same. The first two repeats are over a I chord. The riff is sharp, major-third-ish. On the third repeat, the chord changes to a IV, and I hear the tuning fall down into the pocket of the 7b3. It feels to me as though the IV chord allows George to lock into the 7b3, because that note is its seventh harmonic, a beautiful, consonant note. At that point the song goes blue.
Throughout the song, George goes back and forth between that major feeling (the 3) and that blue feeling (the 7b3), over all three chords. Ear candy.
Now listen to Jimi Hendrix exploring the same kind of space, but around the septimal flatted fifth (7b5). This is a minor blues. The chords are i, bVI and bVII.
There is an insistent riff in Voodoo Child (Slight Return) as well, and it’s a lot like the one in Dizzy Miss Lizzy. The pattern is the same, only moved down and to the right on the lattice.
George Harrison is bending the 2, to get the 7b3 and the 3 notes. Jimi Hendrix is bending the 4, to get the 7b5 and 5. It’s another compact, tasty melody zone. Hendrix explores it incredibly well on this song. He cooks up about a half dozen yummy tritone dishes in the space between 0:30 and 0:60.
If I go back and forth between the two songs, the distinction becomes clear. Dizzy Miss Lizzy is major, and the riff centers around the 7b3. Voodoo Child is minor, and the riffs center around the 7b5. Please do click back and forth between the videos.
Want to hear Eric Clapton and Steve Winwood explore the same territory? Here’s a ridiculously good version of Voodoo Chile (the long one from Electric Ladyland) from 2010.
I’m almost done with the next full-song video. In the meantime, here’s one more pair of mirror twins for consideration.
The 2- is a common melody note in my songs, and in the blues. It goes well with the blue note 7b3 — there is an extremely common melody that goes 7b3, 2-, 1. It’s a darker, more dissonant note than its comma sibling, the 2.
The b7 is dissonant and gorgeous — check out the sequence at the end of this post.
Each note is a compound of three legs on the lattice — two fifths, or a factor of 9, and a major third, a factor of 5. By the logic of the last post, the short leg should predominate, which would make the 2- slightly overtonal and stable, and the b7 slightly reciprocal and unstable.
I’m setting up here for a map of the tonal gravity field. I think I can put some numbers on this stuff. Coming soon. I’ll use that new song animation as a basis — it’s full of fleeting dissonances and polarity flips.
The notes explored so far are 3/1, 5/1, 7/1, 9/1, and their reciprocals, 1/3, 1/5, 1/7 and 1/9. The 9/1 and 1/9 are made up of two legs on the lattice, x3 and x3.
The next overtonal note out from the center is the major seventh, or 7. Its ratio is 15/1, or x3, x5.
The 7 has its mirror twin too, the b2-, at 112 cents. Its ratio is 1/15.
Here is how they sound:
For me, the pattern continues. The 7 is stable, but less so than the notes we’ve heard so far, and it’s getting dissonant as well, because it’s farther from the center. The b2- is both dissonant and unstable.
These notes each traverse two legs of the lattice, a 3 and a 5. The 7 is two legs “up,” or multiplying, and the b2- is two “down,” or dividing.
How will this affect stability and instability? I’ll guess that since 3 is a shorter distance than 5 is, and closer to the center means stronger gravity, the factor of 3 will dominate the blend.
So 3/5, the minor third, should lean toward the overtonal, and 5/3, the major sixth, should lean toward the reciprocal.
This hypothesis is supported by the long tradition that the minor third is a stable note, less so than the major third but OK to end a song with.
That is indeed what I hear, although it’s less clear than it is with earlier intervals.
All four of these intervals use the same prime factors, and cover the same harmonic distance. The difference between them is polarity.
