Music : What is Key ?

Key :

From Merriam-Webster OnLine


Now, all this is fine and dandy. But how do you figure out the key of a progression ?

Suppose, I have the following melody, so to speak

(h - half, q - quarter, e - eighth, w - whole)
(1,2,3 refer to the successive octaves on a piano from L to R)

5Cq - 4Dh - 5Ch - 6Bq - 5Ah - 5Gq - 5Ah - 4Dw

Now, what key is this “melody” in ? Is it even tonal ?

How do you figure out the key of a piece while listening to it ?

And in the same vein, how do you tell if the key changes ?

The full answer would be a little complicated.

Generally, if you look at the last note of a song, that will tell you the key, because melodies have a tendency to end on the tonic. (The first note of a key) Better yet, if you know the final chord of a song, that will usually tell you key and tonality (major/minor).
There are plenty of exceptions but this is generally the case.

Looking at your melody, there’s not enough information for me to really tell you what key it is in. D dorian is a possibility, but it really can be anything depending on what chords you put under it. You could easily make this progression G major if you wanted. Or tonally ambiguous.

It’s easier to figure out key if you can think in terms of chords. What harmonies do you want under your progression? If you can figure out the chord progression, there is usually a base chord you return to, a chord that the progression wants to resolve to, a chord that gives a progression finality. That’s almost always the tonic, and that tells you the key of your progression.

Sorry if I’m crap at explaining this, but I’d recommend picking up a book in basic music theory, because there are a lot of concepts which build on each other to fully explain how this all works.

Yeah, I’ve read this elsewhere, but like you mention, that’s not necessary. But a lot of people listen to the music for about 10-15 seconds and say well, that’s in D minor. How ?

So, this melody by itself isn’t in any key ?

None. Imagine a single voice and a Gregorian chant. Are they in any keys ?

Can you judge this site ? :

It’s not the worst way of explaining music I’ve seen, although I’m not sure introducing tetrachords into the mix at that level isn’t more confusing than helpful. You’ll have to tell us whether it helps you understand things better.

Keys in tonal music (we’ll ignore atonal and polytonal music) are based on a specific scale. So if you have a piece in G major, most or all of the notes in the piece (in both the melody and harmony) will fall onto that scale. If you’re only looking at a melody, you need to see what notes are used, and (as mentioned) what the last note of the melody is as this is usually the tonic (or resting) note, which indicates the key.

originally posted by Gyan9
** Yeah, I’ve read this elsewhere, but like you mention, that’s not necessary. But a lot of people listen to the music for about 10-15 seconds and say well, that’s in D minor. How ?**

Well, sometimes you can just tell if you have a lot of experience with music. For example, right now I’m playing part of a Brazilian-style piece in A minor. The part starts with A minor arpeggeos starting on both A and G-sharp.

Ok. Let’s take G major

The scale is composed using W-W-H-W-W-W-H steps

So, starting with G that is


So, if I substitute C# for C at only one place in a melody in G major, does it change keys ? IIRC, accidentals are allowed. So, how does looking at which notes are used tell you the key, or am I missing something here ?

I get the drift of a key, kinda defines the mood of a piece. So, I guess it would an uneasy cadence if the melody ended on anything other than the root. But how are people able to tell the key of a piece of music before it ends and without looking at the score ?

Gyan9, you may be thinking of someone who has perfect pitch and can identify the actual notes being played without an external reference. Many great musicians do not have perfect pitch. Relative pitch, the ability to determine relationships between notes, is much more important, IMHO.

Also, your comment about the mood of a piece makes me think you might be confusing “tonality” with “key”. “Tonality” is Major, Minor, and occasional others. Key really only refers to the name of the note that is the tonal center of a piece of music. C minor will sound very different from C major.

Not necessarily. If it is clearly temporary, or just a passing note thrown in for flavor, you probably wouldn’t say that a key change occurred. You would need to analyze the surrounding chord structure to make that determination.

However, an entire piece can change keys anywhere it wants to, generally to a closely-related key. This is standard practice for developing a melody. But it almost always returns to where it started.

Not necessarily. In the Olden Days before modern equally-tempered notes, the tones were based on the Circle of Fifths. Nowadays, the ratio of frequencies of two notes a half-step apart is constant, regardless of which two adjacent notes you pick, and all chords have an almost perfect integer ratio of, say, 3:4:5. Before about the time of Bach, though, the tones were set such that in one particular key (I don’t remember which one), all of the chords were in perfect integer ratios. The result of this was that the distortions were larger in all of the other keys, and took different forms. Hence, the different keys did, in fact, have a somewhat different “feel” to them.

Great explanation there Chronos.

Certainly, I personally feel too much emphasis is placed on some occasions on what the key of a piece is. I love nothing more than music which has quirky key changes within the space of 8 measures which gets repeated for the length of the song. Such songwriting results in a delightful melody line which forms the basis for the whole tune.

An example - try this chord sequence…

B flat Major7th
A Minor 7th
D minor 7th
G 7th

By any yardstick, that’s a really pretty sequence, and yet you’d be hard pressed to pick the key. It can’t be F major because G minor is the next chord up from F in the key of F major. See my point? And yet, it’s such a pretty sequence.

And yes, I stumbled upon it myself, but I’m sure I’m not the first to have done so.

For the most part this is right. However, Bach did NOT introduce equal temperament. There is a crucial distinction between well-temperament and equal-temperament. The former is what Bach dealt with. The latter is an late 19th/early 20th century development. Pretty much all composers through the Romantics eschewed equal-temperament. I recall one composer saying that equal temperament is a tuning system in which all keys sounded equally bad.

Keys up through the Romantics did have a distinct feel to them, based on relative ratios between pitches. In fact, several treatises on key, tonality and their corresponding “feelings” and even time signatures were pretty much required reading for musicians of the 18th and 19th centuries. The keys in a well-tempered system were tuned such so they were all playable, yet all retained a distinct character.

As for the C# substitution in the G major scale there, there’s most likely no key change, especially if you use it as a passing tone to the D. If you go on for several measures with the C# taking place of the C, then you have a lot of possibilities as to what your key change is to, depending, once again, on what the tonic is. If the tonic remains G, then you’re still in a form of G major, though a mode called “Lydian.”

I’d talk about modes, but I’m not sure that’s a wise idea at this early point. If you are interested in chanting and Gregorian-style music, then modes may be important for you.

Lets start at the very begining. (a very fine place to start)

Seriously, did you ever watch The Sound of Music?

Anyway you may be familar with the do re mi song. These are notes in a major scale.

You laid out a major scale earlier for the key of G (major).

Although that is the scale for G-M to hear the key you need to listen to the chords


I----G B D (a major chord)
ii---- A C E (a minor chord)
iii----B D F# (minor)
IV—C E G (Major)
V----D F# A (major)
vi—E G B (minor)
vii–F# A C (minor)

Chords as you see can be minor chords or major chords. This depends on the interval between the first note of the chord (calle the tonic) and the second. The I chord (the one chord) is a major chord because the interval between G and B is a major third. The ii chord (the two chord) is a minor chord because the interval between A and C is a minor third.

So when you listen to a piece to determine the key you must listen to the chord progression. No one note can tell you the key. Listen to simple church music. The chord progression is pretty clear. Probably something like I-IV-V-I. Then when you hear the classic resolution of a V to I you know that the tonic note of that chord is the key of the music being played. In the case of a some church music probably the lowest note on the organ is the tonic as the classic way to spell out the chord in this situation would be to put the tonic on the bottom, especially if it is the final chord.
You know a piece has changed keys by listening to the chord progression. When you hear the chord progression ending on a different pitch (same progression) then you know the key has changed.

That’s about the best I can do with out playing records for you.

A silly question, but Merriam-Webster and music dictionaries define chord as three or more musical tones sounded simultaneously.

What if there are no “chords” in the music ? i.e. at most two notes pressed simultaneously on the piano.

Or is a chord inevitable ?

I haven’t got my copy of Piston’s Harmony handy, but AFAIK, that last statement isn’t correct. Two notes can define a chord, and have major, minor, or neutral tonality:

C-C (unison-- neutral)
C-D (major second)
C-Eb (minor third)
C-F (perfect fourth-- neutral)
C-G (perfect fifth-- neutral)
C-Ab (minor sixth)
conversely, C & Ab below is major third

However, one chord can’t define the key of the piece, as there are too many possibilities. A C-E chord might be a major third, but it doesn’t make the key C-major; it could be A-minor, F-major, etc…

I think maybe what Zebra meant was, “you need to listen to the underlying harmony” to determine the key.

Yes for a chord you need at least three notes.

If you are listening to a piano work that only has two going on (a two part invention?) you still get an idea of a chord progression.

Step back and listen to how the notes relate to each other. You can’t just look at the 3 beat of the 9th measure and say whats that. (actually one can but you aren’t at that level yet) Listen to how those notes lead to the next note.

If in your scale of G major you hear the piano play an A and above it an F# you don’t know what chord it is implying. It could be the V chord (D F# A) or the vii chord (F# A C) but if right after it the A moves down to a G and the F# moves up to a G one octave up you now have a pretty strong resolution so you would say the progression was V-I.

So step back and listen to the music and not just the notes.


No. A “chord”, strictly defined, has at least 3 notes. What you have described above are intervals, measuring the distance between only two notes.

The “major” or “minor” in front of an interval is (mostly) unrelated the the tonalities of “major” and “minor” as used to describe a key.

Well, as I said, I didn’t have my harmony book nearby. In any case, I was giving an answer as defined by Gyan9. “No more than two notes” would then be limited to intervals.

ok … clarification time

As I understand it, the word simultaneously means ‘at the same instant in time’. Maaannyy years ago, as a little kid, I was learning the piano. I remember memorizing and playing back with one finger at a time that everlasting melody from Beethoven’s 9th.
Since I used only one finger at a time, were there any chords or harmony involved ?

Did what I was playing have a key associated with it ?

In other words, does key exist independently of harmony ?


No, only one finger = no chords at all or even implied in this particular instance.


Yes, because you were playing a particular bit of music and the key of that is established.

Let me clarify the first two. Could you have a chord with just one note? Well. What if you played the notes C E G. In other words an arpeggio. (sp) You just spell out the chord. It would IMPLY a chord though you did not PLAY a chord.

Now you may know that if you played from C to C on a piano playing only the white keys you would play a C Major scale. Now suppose instead of playing Ode to Joy you just plunked out notes on a piano ONYL TOUCHING THE WHITE KEYS. All of the notes you play occur in the C MAJOR SCALE. Does that mean you are playing in C Major? Not automatically.

There is music that is atonal. This music does not have a key. Even though ‘chords’ are played and implied there is no key.

Suppose Charlotte Church sings Mary had a Little Lamb, she would be singing in a key. It would not matter if she sang solo or if she were accompained by one flute player (so that only two notes are being played at once) or if the London Symphony Orchestra plays along.

So for the final question the answer is Yes Key exists independant from harmony.

So, if key exists within a pure melody, how do you determine the key of a monophonic (term?) melody ?

Well, unless you have an underlying harmony, you really can’t. If I sing C over and over again, I suppose the natural instinct would be to say this song is in “C”, but there’s no reason for me to suppose you couldn’t throw an A minor chord under that. Then I’d be singing the third note in A minor. With no harmonic cues, there’s no way or need to define key in a single-note melody.

By the way, the vii chord (F# A C) in Zebra’s example is technically a diminished chord, which has a flatted (diminished) fifth in addition to a minor third.

Yes, it is possible not to have chords, to answer Gyan9’s question.
You can be purposely tonally ambiguous by leaving out thirds. Usually, if there’s a melody line over a progression of perfect-fifth intervals (as in rock music. Power “chords” are actually intervals of a perfect fifth), then a tonality usually suggests itself. Unless you purposely leave out the third.

There are also harmonies based on intervals of a fourth. These are called quartals, as opposed to tertiary harmony. You hear these mostly in jazz, especially modal jazz and Chick Corea. This is interesting and also tends toward tonal ambiguity since the third is purposely left out. A C quartal chord would be: “C-F-B flat.” It’s a very “open” sounding chord and you can keep tonality ambiguous if you wish.