Why does dropping the 5th sound nice?
December 28, 2013 3:06 AM   Subscribe

When you make a 7th chord, it's common to drop the fifth. We're told it "sounds better," apart from fingering considerations. Why? What is is about the fifth that doesn't go so well when the 7th is in there too?
posted by Opengreen to Media & Arts (12 answers total) 10 users marked this as a favorite
It's possibly just that the voicing is cluttered sounding without doing so. This is why 9th chords are more common than add2 chords, I think - the second clashes with the third, but, if displaced up an octave, it produces a nice, open sound.

Have you ever heard the term "drop 2 voicing"? What you describe is basically an example. The same thing works with other inversions of the chord: lower the second-to-highest note of the voicing an octave.
posted by thelonius at 4:13 AM on December 28, 2013 [1 favorite]

Spaciousness and softening. Dropping the fifth (leaving 1,3,7) emphasizes the major/minor aspect of the chord, rather than the (stronger) perfect fifth. It also better implies / allows for tritone substitution.

By contrast, using just the 1,5 (the power chord) allows blurring major and minor (metal, blues).

Another practical bit: In group settings, the bass often fills in the 1 and 5. Two instruments playing the 5 is a lot of 5 (old timey, bluegrass) and feels very "major".
posted by gregglind at 5:30 AM on December 28, 2013 [3 favorites]

Two historical explanations:
1) It's a left-over custom from traditional voice leading, and is not about about that this chord taken by itself sounds "better" when the fifth is left out. If you imagine a dominant seventh chord on C (for example as the dominant of a cadence to F, in a baroque choir setting, or continuo or something), the bass would likely sing the lower C, the tenor the upper C, the alto E, and the soprano B flat. Resolving to: Bass (upward) F; tenor (same) C; alto (upward) F; soprano (down) A
Now, as an alternative, the bass and the tenor could be written higher (bass high C, tenor E), leaving the "missing" G to the alto. But when resolving this to the F tonic, it results in the tenor still having to resolve upward to F, while the alto needs to go downward, also to the same F, which reduces the number of effective voices in the final chord (the alternative, bass resolving from the higher C downward to F and the alto from E downward to C results in a not-hot parallel downward leap into a fifth, so we avoid that kind of thing).
When you play continuo from a figured bass you continuously think ahead two or three steps to prevent this kind of crunches from happening.

2) Focusing on a "better" sound, the explanation actually goes even further back in time, to quarter comma meantone tuning, which is based on pure major thirds and heavily tempered fifths (with a few exceptions). We're talking about late Renaissance and early Baroque keyboard music; the fifths are bearable albeit somewhat sour, but the major thirds sound altogether pure and clean; one does find voice leading solutions in that style that favor major thirds and avoid fifths.
posted by Namlit at 5:53 AM on December 28, 2013 [1 favorite]

The standard "authentic" cadence is V-I. In traditional harmony, the most used chord sequence is I-IV-V-I. Our ears hear each chord as being "pulled" toward the next one.

The most common alteration is to add the 7th, giving I-IV-V7-I. The dissonance of the 7th makes it pull harder toward the resolution on the I chord. To understand the "pull toward resolution," play I-IV-V7 and walk away.

The 5th is consonant with the root and the 3rd. The 7th is dissonant with the root and forms a tritone with the 3rd. By dropping the 5th, you have one less harmonic note and thus the tritone and dissonance are more prominent, making the pull toward I even stronger.

Dropping the 5th thus makes it "hurt more," so that it "feels so good when you stop" by resolving to I.
posted by KRS at 5:56 AM on December 28, 2013 [2 favorites]

I took an awful lot of music theory when I was getting my degrees, and don't recall ever hearing this. So I wonder (a) who told you this, (b) whether they were coming from a classical, jazz or pop perspective, and (c) what instrument they were talking about?
posted by slkinsey at 6:31 AM on December 28, 2013


Fair question.

I've heard this in many places, but here's one I have right in front of me: "The Pocket Idiot's Guide to Piano Chords," by Karen Berger, pp. 99-101.

On p. 101, the author writes, "Another way to simplify the dominant seventh chord is to play three of its notes. But which three? . . . . The two notes that are left are the third and the fifth. Of those two notes, most pianists choose to keep the third. . . The reason is that the third is the note that determines whether the character of the chord is major or minor. The fifth, as it turns out, is the most dispensable. . . "

But I didn't think that explanation was convincing, which is why I asked askmetafilter.

Thanks everybody!
posted by Opengreen at 7:08 AM on December 28, 2013

I took an awful lot of music theory when I was getting my degrees, and don't recall ever hearing this. So I wonder (a) who told you this, (b) whether they were coming from a classical, jazz or pop perspective, and (c) what instrument they were talking about?
For what it's worth, I (pianist with a lot of music theory) didn't hear this until I started studying jazz. Here's Mark Levine in Chapter 3 (Three-Note Voicings) of The Jazz Piano Book, for example:
Remember, the fifth is not as important because each chord has a perfect fifth (there is an exception to this -- this half-diminished chord -- which we'll get to in Chapter Five). Three-note voicings reduce most chords to three essential notes: the root in the left hand, and the third and the seventh in the right hand.
He then proceeds to illustrate the standard ii7 - V7 - Imaj7 jazz progression with three voices.
posted by dfan at 8:28 AM on December 28, 2013

Also, the fifth is usually a prominent harmonic overtone in the root note anyway, so it will be there as part of the root note.

(Guitar string harmonics: frets 12 and 5 make the root note one and two octaves up respectively; fret 7 makes the fifth between them. When you play the note, all of those harmonics are present to some degree, so the fifth is heard even if you don't play it.)

(Yes, the fifths of the other notes will also be present, it's madness. I suspect that the harmonics of the bass note will be more prominent. Anyway, this is what I was told.)
posted by Grangousier at 8:41 AM on December 28, 2013

Also check out this chart that shows how the overtones of a note line up with the different intervals of a chord. The 5th shows up in the third overtone. Since lower overtones are usually stronger, this means the root note will already contain a lot of the same harmonic content as the 5th. In contrast, the thirds and sevenths show up later in the harmonic series, and in higher octaves, where they are less prominent. So there's less "overlap" between the root and the 3rd or 7th.
posted by scose at 9:30 AM on December 28, 2013

All of the above explanations make sense, but I would remind you that the 'rules' are still just suggestions. Keeping the 5th in your dominant 7th chord creates a certain sonic effect and who's to say you won't find a place where it works perfectly. Off the top of my head, if I was playing C7 on the piano and putting the dominant 7th (Bb) in the bass I would usually tend to put the fifth (G) in the right hand and maybe even drop the third. Those strong tones of root and fifth help announce the chord as a C7 even though the most dissonant chord tone is in the bass. Ditto if you're putting the third (E) in the bass.

Try everything and see what sounds best, basically.
posted by TheRedArmy at 9:58 AM on December 28, 2013

Also, the fifth is usually a prominent harmonic overtone in the root note anyway, so it will be there as part of the root note.

This is really at the heart of the answer to this, though it would be more correct to say that the fifth is always a prominent harmonic overtone. I'm not sure about it "sounding better" in a qualitative sense, but the reason the 5th frequently gets dropped from harmony-centric music (like jazz) is because the 5th is more or less color on a chord - it (generally) serves no distinguishing purpose in the harmony of the chord. The harmonic function of a chord in tonal, western harmony is determined by the root, third, and whatever extensions, excluding the fifth. It's not so simple to say this is entirely due to overtones, because there is definitely a learned/cultural aspect to it as well, but it is definitely a significant part of it. The fifth is a prominent overtone, unlike the 3rd and 7th.

There's something to be said for the notion that there is a sense of implication of the fifth whenever you're working within a tonal system which is established by the overall gestalt of the music you're playing. The primacy of the tonic-dominant function can be said to be the entire basis of Western harmony. If you've listened to a lot of classical music and jazz, you're more apt to be listening to the music from within that context, and you'll more or less fill in the 5th with your brain (no joke), unless presented with some unexpected variation on the 5th, like a diminished 5th or such. It's a bit of the nurture/nature thing.

So you can drop the 5th and it's still implied. This allows you to either play more efficient voicings, or to highlight other harmonies in the chord without coloring the whole thing with the 5th, which will tend to dampen or round-out the entire harmony more than you might want.
posted by Lutoslawski at 12:20 PM on December 28, 2013 [1 favorite]

An interesting way to think about this is phone calls. You only need some and certain overtones to perceive a pitch. You don't even need that actual pitch. Phones strip out any frequencies under 300Hz, but you still get the overtones, and your brain fills in the fundamental. It's why you sound a little weird on the phone. The pitch isn't different from your regular voice (even though the frequency make-up isn't the same), but the timbre is much different.

It's a similar thing in harmony. Dropping the 5th won't change your perception of it's implication, but it will change the timbre of the sound, which you may or may not think sounds 'better.'
posted by Lutoslawski at 12:29 PM on December 28, 2013 [1 favorite]

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