- This topic has 3 replies, 4 voices, and was last updated 7 years, 3 months ago by .
-
Topic
-
The last in this series on intervals involves sevenths. There are two types of sevenths, major and minor. Neither of them appear in the harmonic series. The closest is the seventh partial, and it is far enough away that it simply is not used in Western Harmony or melody.
Rather, the sevenths are derived intervals. We get to them by inference from other intervals, and not directly from the harmonic series as we do with octaves, fifths, and thirds.
Major Seventh
The major seventh is arrived at by putting a major third on top of a perfect fifth. It is eleven semitones, or eleven frets on the guitar. In just intonation, it has a ratio of 15/8. The just intonation major seventh is a smaller (flatter) than the equal tempered major seventh.
It is not often used melodically, but it is the opening interval in Don’t Know Why I Didn’t Come by Norah Jones.
For a descending major seventh in a melody, the only example anyone gives is from Cole Porter’s I Love You.
Minor Seventh
The minor seventh is also a derived interval. There are two ways to get to it. It’s either a minor third on top of a perfect fifth, or it is the distance from the 2nd to the Octave. It is 10 semitones or half steps, which means 10 frets on the guitar.
The minor seventh interval is especially important in blues, because the minor seventh is the fourth note in the minor pentatonic scale and is the first of the “blue” notes. Adding a minor seventh to a major chord makes the chord a dominant seventh chord, which is the cornerstone of all twelve bar blues (and 8 bar blues).
In just intonation, a minor seventh is either 9/5ths ratio or 16/9ths. It’s considered a dissonant interval, and it does not appear naturally in the harmonic series. The seventh partial harmonic is a little sharp of the dominant seventh. (If you play with bending the dominant seventh a little, you might find that partial harmonic, which can sound strangely satisfying.)
It is another interval that is rarely used in melodies. One famous example is from Somewhere from West Side Story.
For a descending minor seventh, maybe the most famous example is from Herbie Hancock’s Watermelon Man:
Compound Intervals
There is no reason an interval has to be an octave or smaller. An interval can span more than an octave, and in theory at least, can span several octaves. The limit is only the range of human hearing.
An interval larger than an octave is called a compound interval. You will see them a lot in jazz harmony. The only ones that are used in practice are the 9th, 10th, 11th, and 13th.
To translate these intervals into more familiar terms, simply subtract 7. Thus, a ninth is a second, but up an octave. The 13th is a 6th but up an octave.
The 9, 11, and 13 are used because they are upper extensions of a chord. In western harmony, chords are built by stacking thirds. Thus, basic chords have a 1, 3 and 5. Seventh chords, like the dominant seventh have a 1 3 5 and 7. If you keep going in this process, you get a 1, 3, 5, 7, 9, 11, and 13. (The 15th is simply the Octave doubled, so it doesn’t get an interval name.)
The tenth is also commonly named because it is a basic interval for piano players (or those who have slightly larger hands than I do). When playing stride piano, which was an early jazz style, pianists like Fats Waller would very often play an open tenth in the left hand, on the first and third beats, with a chord on the offbeats.
Duck Baker uses tenths to great advantage on his version of Blue Monk:
I think the reason we don’t get names for intervals like a 12th is because a player would just consider it a fifth, since its not an upper extension, and pianists don’t use it because very few of them have hands big enough to reach that far (Van Cliburn was an exception, with truly gigantic mitts).
Next up, we can start looking at chords.
- You must be logged in to reply to this topic.