why is the 3rd the note that determines major or minor?

[bobsguitars09]

why is the 3rd the note that determines major or minor?

[randalljazz]

that's the definition. chords are built by stacking thirds--every other note in a scale. root is assumed. fifth is presumed P5. 7th and above are not relevent at this stage. minor 3rd (from the minor scale), with root and 5th = minor triad; major 3rd (from major scale), with root and 5th = major triad.

if you want a deeper explanation that "that is the definition", i would invite you to study about the history of western music, and how we came to have the major/minor system. a fascinating story, spanning about 1200 years or so, from about a.d. 500 to about 1700. donald grout history of western music is a good place to start.

[Little Jay]

Because - to ears shaped in our culture - a flattend (or small, the meaning of 'minor' in Latin) third in a chord (3 stacked notes) sounds sad and a natural (or big, the meaning of major in Latin) third in a chord sounds happy .

[bobsguitars09]

Thanks!

[Baltar Hornbeek]

why is the 3rd the note that determines major or minor?

Just keep playing it, I think you'll eventually hear it. Sing it too.

[BigDaddyLoveHandles]

Come to think of it, why is it the "Blues" and not the "Teals"?

[timscarey]

Two reasons that are actually the same reason.

Let's use E as our root or fundemental.

The 5th overtone in the series from an E root is the note G# (its a few cents flat from the tempered system) to hear this, play the open low E on your guitar, then play the 4th fret harmonic on that string. You will hear low E, then G# a few octaves higher.

Now, because these overtones are present in the fundemental, adding a G# supports the natural overtone creating constanance or "majorness" if a G natural is intruduced, dissonance is created because the overtones of the fundemental are at odds with the G.

The quick answer is.... harmony is just ratios of vibrational speeds between notes. The ratio for a major third is 5/4 and the ratio for a minor third is 6/5. The wider the ratio, the more constanant the interval.

A fourth is 4/3 a fifth is 3/2 and an octave is 2/1.

We just call those sounds major and minor afterall, the third is just an interval, its the whole triad that creates the actual major or minor sound in its entirety.

[Aristotle]

An interval by any other name.

And why is it a pefect and diminished fifth instead of a major and minor fifth?

[BigDaddyLoveHandles]

And who came up with "shave and a haircut, two bits"?

[guidoscope]

An interval by any other name.

And why is it a pefect and diminished fifth instead of a major and minor fifth?

In diatonic scales the fourth and fifth interval appear in three variations: perfect, diminished and augmented. The other ones in two variations: major and minor.

[BigDaddyLoveHandles]

In diatonic scales the fourth and fifth interval appear in three variations: perfect, diminished and augmented. The other ones in two variations: major and minor.

Major 7th: G-F#
Minor 7th: G-Fnat
Diminished 7th: G-Fb

This is not just speculative theory. The diminished 7th is used in a diminished seventh chord:

Gdim7: G Bb Db Fb

[guidoscope]

Major 7th: G-F#
Minor 7th: G-Fnat
Diminished 7th: G-Fb

This is not just speculative theory. The diminished 7th is used in a diminished seventh chord:

Gdim7: G Bb Db Fb

Yes, but I was talking about their appearance in diatonic scales. But the diminished seventh interval as well as the augmented second also appear in both the harmonic major and the harmonic minor scale, come to think of it. So my answer doesn't seem to be correct indeed.

[ejwhite09]

Not to start anything, here, but sometimes it seems like people stop by the forum, and ask questions, that can be answered by reading some of the ridiculously informative and understandable articles and lessons, dirk goes through, im sure great pains, to put together. Just at though...maybe look for the answer on the site, then come to forum.

But yeah, most people answered the question wrongly. The answer is kind of technical and has to do with those frequency ratios. To be honest, it's completely unnecessay to know WHY a major third 'resolves' and a minor third does not, but needless to say it is the lack of resolution in the minor third interval that causes dissonance that causes auditory instability that makes the interval sound troubled, we perceive this 'troubling instability' as 'minor' its 'triumphant, resolving, reassuring' counterpart as 'major.'

[ejwhite09]

In diatonic scales the fourth and fifth interval appear in three variations: perfect, diminished and augmented. The other ones in two variations: major and minor.

Major/minor
Major and minor intervals are so-called because certain diatonic intervals (seconds, thirds, sixths, sevenths, and their compounds) may occur in two sizes in the diatonic scale. The larger of the two versions is called major, the smaller one minor. For example, the third occurs both as three semitones away from Re, Mi, La, and Ti in the major scale (or in the C major diatonic scale, three semitones above D, E, A, and B), and four semitones away from Do, Fa, and Sol, (or C, F, and G). The smaller, three-semitone version is called the "minor third" and the larger, four-semitone one is called the "major third". Major intervals invert to minor ones, and vice-versa. For example, a major second inverts to a minor seventh, and the reverse.
Perfect
Perfect intervals are so-called because of their high levels of consonance, and because the inversion of a perfect interval is also perfect. Other kinds of intervals have an opposite quality with respect to their inversion. The inversion of a major interval is a minor interval, the inversion of an augmented interval is a diminished interval. Within the diatonic scale all fourths and fifths are perfect, with five and seven semitones respectively, except for one occurrence each of six semitones: the fourth between Fa and Ti (an augmented fourth), and its inversion, i.e. the fifth between Ti and Fa (a diminished fifth).
Augmented/diminished
Augmented and diminished intervals are so called because they exceed or fall short of either a perfect interval, or a major/minor pair by one semitone, while having the same interval number (i.e. encompassing the same number of staff positions). Except for the augmented fourth (Fa-Ti) and diminished fifth (Ti-Fa), they do not appear in the diatonic scale. For instance, there is no three-semitone interval in the diatonic scale that functions as a second, and the augmented second (e.g., E?–F?) is three semitones wide.

[ejwhite09]

So you kind of have to think of intervals, OUTSIDE of the scale. Then apply intervals to BUILD a scale. Analyzing intervals as part of a scale per se, is kind of missing the point of them. It's kind of like atoms and molecules, scales are molecules, they are comprised of something that already was independent and unique which combined to form a molecule. An oxygen atom, is an oxygen atom, you don't analyze it from the point of view that its just a part of a water molecule. An interval is an interval, in and of itself. As we combine oxygen with hydrogen we obtain a water molecule. As we combine major, minors, perfects, diminished, and augmented intervals we build scales. In fact when you really get the point of intervals and scales, you can pretty much stop caring about learning scales, because you in essence can build scales in realtime to deliver the sound you need, this is why so many 'greats' often say 'they don't know they're doing.' You don't need to know the third mode of the lydian dominant scale, if you know what sound you want to hear, and you know what interval combination will yield it, then yes perhaps they did just blow your mind with the third mode of the lydian dominant scale, but they can't articulate that, because they don't spend time, finding out what the third mode of the lydian dominant is.

[guidoscope]

For instance, there is no three-semitone interval in the diatonic scale that functions as a second, and the augmented second (e.g., E♭–F♯) is three semitones wide.

By my knowledge the diatonic scales are:
major, harmonic major, melodic minor and harmonic minor. (the 7 tone scales that have a dominant 7 chord a perfect fifth away from the root and do not contain two consecutive half tone steps)

And both the harmonic major and the harmonic minor contain an augmented second interval and a diminished 7th. (if there is a augmented second, there has to be a diminisched 7th and vice versa of course) For instance in C harmonic minor, the distance between the Ab and the B is an augmented second.

I believe we should be speaking about the appearance of the intervals in the diatonic major scale (and its relative modes), then there are no exceptions that break the rule.

[tjmicsak]

The major and minor 3rds also have a reciprical in the major and minor 6ths, which are the same notes reversed, root over third.

[woyvel]

I've understood chord theory for a long time. Just passed the Berklee chord game with flying colors, but now my head is spinning.

[Patrick Brown]

And who came up with "shave and a haircut, two bits"?

That may derive, and correct me if I'm wrong, from the Limerick type (hate to call it a poem), that rhymed with 2 A parts, 2 B parts, and ending with the final A part that had the more or less same syllabic structure as 'shave and a haircut...'

[Robertkoa]

To the OP - there are better technical explanations than this one, but music and music theory in general exploit or take advantage of natural physical properties of sound waves- the overtone series being one of the main laws or phenomena having to do with harmonics , and consonance and dissonance, and rhythm and when we play intervals or notes simultaneously we are taking advantage of these* natural laws and Major/ Minor in combination with standard practice and learned responses is one of the offspring, you might say ( so is Blues and Funk Music, and Disco ha ha ).

* However , when the advanced beings or God created the Big Bang ( and all the Laws of the Universe ) - even THEY did not realize Disco was a possible result.