Seventh
A musical interval: the distance between two tones that
are seven tones apart.
[Example 1: Mozart Requiem: No.8 Domine Jesus Christe, "Ne absorbeat eas Tartarus," CD2707]
The seventh is a musical interval. It comprises two tones that are seven tones apart. That is to say, it is one tone less than an octave.
Types of Seventh
There are two principal types of seventh: major, and minor.
Here, first, is the sound of a major seventh, played successively (as in a melody), then simultaneously (as in a chord):
[Example 2: major 7th: (1) successively, (2) simultaneously]
Notice how harsh the major seventh sounds when played simultaneously [Example 3]. The interval is extremely dissonant.
The minor seventh is only slightly less harsh than the major:
[Example 4: minor 7th: (1) successively, (2) simultaneously]
The minor seventh is still dissonant when played simultaneously [Example 5], but the dissonance is not quite so intense as that of the major seventh.
(Incidentally, note that all musical intervals are counted inclusively. That is, the first and last notes are both counted. As a result, all intervals comprise one step less than their number might seem to indicate. A seventh thus contains seven tones, but only six steps.)
There are two other kinds of seventh: the diminished seventh, which sounds the same as the major sixth; and the augmented seventh, which sounds the same as the octave. The latter two occur mostly in music whose style is chromatic.
The Role of the Seventh in Melody
The seventh is a wide interval, and is awkward to play or sing. Consequently, its role in melody is limited. If you know the song "Somewhere," from Westside Story, sing to yourself the opening phrase ("There's a place for us"). The first two tones form a rising minor seventh.
The seventh is used to special effect in Mozart's Requiem (featured dramatically in the film Amadeus as the music that Mozart writes on his deathbed). At the words "Lest they be devoured by Hell, lest they fall into oblivion," Mozart makes his singers plunge down a succession of sevenths, which vividly suggest souls plunging into the abyss. Listen to the music, and see if you can follow it on the diagram.
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Fig 1: Mozart Requiem: "Ne
absorbeat eas Tartarus ..." |
[Example 6: Mozart Requiem: No.8 "Ne absorbeat eas Tartarus"]
This jagged and dramatic line is sung there by the tenors. It is then sung three more times by the other groups of the chorus, to form the beginning of a fugue. See if you can follow the four groups in turn, with the orchestra chugging away beneath them: tenors-altos-sopranos-basses. Watch the next diagram as you listen.
[Example 7: Mozart Requiem: No.8 "Ne absorbeat eas Tartarus"]
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Fig 2: Mozart Requiem: "Ne
absorbeat eas Tartarus ...": four fugue
entrances. |
Sevenths in a Tug of War!
When sounded simultaneously, the two tones of a seventh produce a pungent effect. That is (as we saw earlier): simultaneous sevenths are dissonant. In tonal music, when a seventh sounds between two simultaneous tones, one of those tones is exerting a strong attractive force on the other. This diagram - in which squares represent tones - shows two melodic lines, each only three tones long.
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Fig 3: 6-7-6 attractive force. |
The first and third pairs are a sixth apart. The sixth is a consonant interval, so no tension exists between those pairs, at the beginning and end. However, line 2 moves down one step between tones 1 and 2, while line 1 stays still. This increases the distance from a sixth to a seventh - a dissonant interval. The result is a tug of war. Line 2 pulls line 1 toward it; and in response, line 1 moves down a step between tones 2 and 3. This is how this sounds.
Baroque composers love to use this device - the technical name for which is a suspension - and to join several of them together in a long chain. Here, English composer Henry Purcell strings four of them together, then relaxes, strings four more together, relaxes again, and strings yet four more of them together before coming to a halt. Listen to the whole passage, and try to follow it on the diagram. All this dissonance produces a heavy, dragging effect, which by the third time sounds anguished.
[Example 9: Purcell: Sonata No.2, Adagio, CD 2077]
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Fig 4: two chains of four 7-6s. |
Chords with sevenths in them are among the most powerful effects in tonal music. This power is the ability of the seventh to propel the music in a particular direction - to move it into a new key, for example. The two most important of the seventh chords are the dominant seventh chord and the diminished seventh chord.
Many jazz musicians use sevenths liberally to enrich and intensify their harmonies. Here, the tune "Sweet Georgia Brown" is accompanied by quiet, stabbing seventh chords of various types.
[Example 10: "Sweet Georgia Brown";:Junior Mance, CD 1022]
Summary:
- A seventh is an interval comprising two tones that are seven tones apart; that is, one tone less than an octave.
- There are two normal sizes of seventh: major and minor.
- Both of these are dissonant.
- The seventh is wide, and awkward to sing, and is sometimes used to achieve special effects.
- Played simultaneously, sevenths are a principal source of dissonance.
- In Baroque music they are often used in chains called suspensions, which may be used for expressive effect.
Note: Having learned about the seventh, you may want also to consult the definition of the Second, since the second is closely related to the seventh (they are in fact the inverse of one another), and the two behave quite similarly.
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Visual & Sound Materials from the Gabe M. Wiener Music & Arts Library of Columbia University | |
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Seventh written by:
Ian Bent Recording & Mixing: Terry Pender & Christopher Bailey |
Narration:
Ian Bent Technology & Design: Maurice Matiz |