I know next to nothing about musical theory. Torturous, mandatory participation in musical endeavors in youth taught me how to read music and the very fundamentals.
Why does changing the number of sharps and flats in the key so dramatically change the entire sound of the piece? Why is the key so important that famous pieces of music are billed as “Such and such in G major” or whatever?
I mean I know that some of the notes will be half a step higher or lower depending on what the key falls for. But I can’t imagine why that changes so much. I’ve heard songs like The Star Spangled Banner and other famous works played in a minor key and it completely changes the entire sound. How?
In: Culture
There’s two very important difference between “minor” intervals and “major” intervals that are hard to see just from how close they are to each other.
First and probably most important: Changing an interval will also change where the note will want to go. Major intervals tend to be very stable so they are comfortable being where they are, and if they do show any “desire” to go anywhere then the direction that they want to go tends to be up. (not always but it tends to be). A minor interval is generally less stable than a major interval (not necessarily dissonant but definitely less stable) so they have a stronger tendency to “go somewhere else”, and that tendency tends to drop them downward.
Imagine a very small melodic passage over imaginary notes that we will call 1 2 and 3. If your melody is “1 2 3” then we can very heavily change the “character” of our melody by changing what note 2 “wants”. Going 1 2 3 over a stable “2” note that kind of wants to rise up is going to give a very different character than going 1 2 3 over an unstable “flat 2” that really really wants to drop down.
A second and more advanced difference between minor and major intervals is that their harmonic character changes a lot more than what their small difference in frequency suggests. The notes notes might only be one semitone apart, but our harmonic experience isn’t dictated in the plane of semitones, but rather it is dictated on a plane of elegant harmony of frequencies that vibrate either at double, triple or quintuple each others frequency. I don’t think I can really ELi5 this so instead let me compare it to a knight in a game of chess. The knight does not move in single steps, but rather it takes these large leaps that are sort of “L” shaped. If I have my knight in square K5 and I want my knight to move to square K6 then you might go “that should only take one move, because it’s only one square next to him”. But the knight doesn’t move that way, so it’s going to take him several moves just to end up in the square next to him.
Harmony is kind of the same way, it does not move in simple steps of a semitone, so it needs to take several “turns” to end up in a square that looked like it was right next to them. As a simple example: There might be twelve semitones between the note C and its higher octave (also C), but it only takes one harmonic “turn” to move between the two, because their frequencies differ by an elegant multiplication of 2. So the third C on your piano and the fourth C are going to have near identical character; they are only one harmonic “move” away from each other. Meanwhile the difference between C and C#, while seeming very small, is actually three harmonic “moves” away from each other.
The difference between a major and minor interval is in fact so big on the harmonic plane that they could be considered different “generations” of origin. The note D could be considered the “son” of the note C (that is to say, the note D originates from the natural resonance of the note C) whereas the note Db could be considered the “father” of the note C (that is to say, the note C exists in the natural resonance of the note Db, but not the other way around). Melodically speaking the notes Db and D are so close to each other, but harmonically they are so far away.
First of all, lets explain what exactly is “a musical key”.
A key has two main elements:
1. The tonal center, which is the particular note that feels like “home” or where the songs resolves to.
2. The quality, which is either major or minor.
#Tonal Center and Pitches
Is you listened to a song you’ve never heard before that has C as its tonal center, you wouldn’t be able to tell it is in C unless you have perfect pitch, and that’s quite uncommon. If we waited a day and played you the very same song but this time we used D as the tonal center, you wouldn’t be able to tell the difference.
Why? Because the current musical system uses a particular way to tune instruments known as *equal temperament*. The gist of this tuning system is that [the interval (musical distance) between two pitches is given a specific ratio](https://en.wikipedia.org/wiki/Equal_temperament). So, it doesn’t matter which tonal center you’re using, if you’re conserving the intervals, the songs will sound the same.
Back then, there used to be a different tuning system, where the intervals and ratios between pitches weren’t the same. Thus, each key had its own distinctive character. But with the rise of equal temperament, that character disappeared.
A video that talks more about this:
* [Adam Neely, Which key is the saddest?](https://youtu.be/6c_LeIXrzAk)
#Tonal Center and Instruments
You mentioned that you used to play an instrument, so I’m sure you know that each instrument has a natural musical range and, given how the instrument is built and tuned, some notes are easier or harder to play. As such, some particular tonal centers fit better with certain instruments because they’re easier to play or you have access to some particular notes.
For example, the standard tuning for guitar is on E. The lowest note on a guitar is E so, having access to that particular note drives guitarists to play more “E-based music”. If you go back to your music sheets, you’ll notice that violins have more songs “in D” than, let’s say, songs “in Eb”. Why? Because D is easier to play on a violin, considering that one of the strings is tuned to D
#Major vs Minor
This difference is easier to tell than tonal center. You can easily guess if a song is major or minor because major feels upbeat, bright and happy, whilst minor sounds darker and sad.
The change in perception most likely comes from the fact that in a major key the notes have bigger intervals between them (at least the important notes), compared to minor keys. For example, the interval between C and E (major third interval) is greater than the interval between C and Eb (minor third interval). It seems like this is at the core of the issue, because even throughout cultures, the intervals related to the Western minor key have a similar connotation.
A video that talks more about this:
* [Adam Neely, Why is major happy?](https://youtu.be/9rEqrPwVITY)
When you hear music, you hear two things. The note, and the distance between the note and the next note (and next note and so on). Music written in a certain “key” will sound as it sounds because we hear the notes, and intervals, as they were intended.
Changing the key, otherwise known as “transposing,” will change the note BUT WILL NOT change the interval between notes. Thus, the piece will still be recognizable. They “sound different” because the notes are different, each note having its own rich overtones and undertones. But
However, when you change keys into a MINOR key (from major, or vice versa), you have changed (some of) BOTH the notes and the intervals between the notes. The piece of music will thus sound different. A half-decent ear could still “pick out” the original piece of music, as the original (especially if we have enjoyed it/listened to it many times) will still be in our memory. But the sound colour is fundamentally different.
When you play a piece normally in a major key in a minor key instead, it completely changes the melody. You are changing *some* of the notes played, but not others. This results in a very different sound.
You can also *transpose* a piece – that is, shift *every* note up or down by the same amount. An example would be playing a piece in C major in F major instead. This *might or might not* change the sound significantly, and the reason is tuning.
Tuning is the relationship from one note to the next. Prior to the 20th century, many different kinds of tuning were in use. The distance from C to C# was *not* the same as the distance from F to F#. Thus, if you played a piece in C major in F major instead, you would once again be changing the melody because the relationships between the notes would be different.
In the early 20th century, *equal temperament tuning* became almost universally used. This is a tuning where the ratio from one note to the next is always the same, no matter where in the scale those notes are. Thus, transposing from C major to F major would not significantly change the sound of the piece, because the relationships between all notes would be the same; the piece would just be played higher.
However, playing a piece higher or lower than usual *can* change the sound a bit, because notes in a very low or very high register get perceived a little differently. A piece which is normally played around middle C would sound quite menacing if played several octaves lower, even though the notes are the same; and quite shrill and chintzy if played several octaves higher.
I’m going to try to actually ELI5 here, at least more so than the other replies, which all seemed incredibly technical.
Major keys vs minor keys are kind of like happy vs sad…both are acceptable, but very different. Songs in major keys sound much happier than songs in a minor key do, so if you want a song to sound sad or serious, you want it to be played in a minor key. There are exceptions to this rule, but in most cases we hear music as major=happy and minor=sad. Culturally we use major songs to represent happy occasions and minor songs for sad ones, and that is the biggest reason I can think of to explain why we attribute emotions to songs that might not be specifically meant to be emotional.
Tempo and rhythm can also both affect the overall “feel” of a song as well, the key is not the only factor involved in how we perceive music.
Changing between related keys, like G major to C major (known as transposing), won’t actually make that much difference; It’ll sound the same, just higher or lower than before, like when you play a song faster. This is because the distance between the frequencies hasn’t changed.
However, going from G major to G minor will definitely make a difference since you’ve changed the scale it’s played on and thus, the distance between the frequencies. The way these frequencies interact (harmonize) is what makes them sound happy (major), sad (minor), etc.
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