In most cases (if not all), a piece of music without sharps or flats in the key signature, would be considered in the key of C major or A minor. This question assumes the context of Western Music since that is the only type I know much about.

The key signature defines which notes (in the absence of accidentals) are available to include in the composition. So obviously if the key signature has no sharps or flats, any note written on the staff will be one of C D E F G A or B (all natural), which are the notes in the key of C major and also its relative minor (A minor).

But if we change the tonal center from C to another note, without changing the available notes, then we are in a different mode. For example if we start on F and play a scale using all the notes in C major (resolving back to F), I believe that would be considered the F Lydian Mode (even though the notes are all common to the C major scale and derived from the key of C major).

So does that mean that F Lydian Mode actually belongs to the key of C? Similarly does each mode in the chart below (all comprised of the notes found in the key of C major/A minor) belong to the key of either C major or A minor? Certainly the key signature would indicate as much.

I know that the Aeolian Mode is equivalent to the A natural minor scale. This makes me believe that modes must be defined as being derived from either a major or minor parent key.


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    Interesting question! I ponder as to whether a piece, say, in F Lydian, should have the key sig. of the parent (C) or the key sig. of F (a Bb) with all the Bbs in the tune marked as B naturals.
    – Tim
    Commented Jan 20, 2016 at 7:39
  • I personally try to avoid using the word 'key' at all if I want to communicate clearly and unambiguously - it's overloaded (meaning different things in different contexts), and in some of those identifiably distinct meanings is still vague. Commented Jan 20, 2016 at 13:36
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    @topomorto most musical terms are overloaded like major, minor, and even the notes. IMO key is a lot easier to convey then the diffrence between the concept of a note used in a set (like the notes of a scale or chord) and notes on the staff.
    – Dom
    Commented Jan 20, 2016 at 13:42
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    @topomorto every subject has terminology. It's needed to convey the subject matter. Math and science has similar overloads especially when you get into the different subsections of each and music is not alone with this issue, but even though you may not like you should use these terms else you get what we had with the "tonal centre" question.
    – Dom
    Commented Jan 20, 2016 at 14:17
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    @ToddWilcox I clicked the link and found that the top rated answer contained this "as opposed to the C-minor scale, or one of the other scale-modes based on C". Which is the basis of my question - is F Lydian one of the scale modes based on C? Or is it based on F? Certainly this question has stimulated many lively discussions ;-) Commented Jan 20, 2016 at 19:09

8 Answers 8


No. A key* is not just a set of notes, it tells you the tonal center** of a piece and the expected harmony and melody of the piece. If that was the case we wouldn't even distinguish between major and minor as they have the same set of notes as do all 7 modes of the diatonic scale. How you use your harmony and melody will define the key and tonal center by making one note sound like it is more at home than the others.

Take this simple progression that would be more at home in F Lydian rather than C major:

FM7  Dm   Em   C

In general the harmony of Lydian and Major(Ionian) are pretty similar with the distinction being the augmented 4th (in this case B) which will typically come out in the melody and harmony. We start on an F chord and we end on C which takes us right back to F so we feel F as the tonal center. In analysis we would denote this as:

FM7  Dm   Em   C
I7   vi   vii  V

If we truly perceived C as the tonal center in this progression the analysis would yield:

FM7  Dm   Em    C
IV7  ii   iii   I

We're now looking at the progression as in "the key of C" and it may work in some contexts, but calling F the tonal center makes much more sense. You would want to end your progression on an F major chord.

*Typically when you talk about a key you talk about tonality and typically use the terms major and minor rather than modality and refer to the modes themselves, but the idea is still there.

**Even the phrase "tonal center" when apply to modes is a little fuzzy strange to apply to modes as the tonal refers to tonality, but for continuity I'll use tonal center to describe modes too. Here's an in depth explanation about tonal vs modal for more background about the difference.

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    @Dom Two points to mention: 1.) I think if you play through your progression, you won't hear it relative to "F" as a tonal center. The raised 4th incidentally turns the "G" chord into a secondary dominant, which naturally leads to C. So, I don't buy that your progression is "more at home in F Lydian". 2.) I think you should make the distinction between "keys" and "pitch collections". While you're correct that the two are not the same key, the OP's basic premise is actually correct; despite different tonal centers, they share the same pitch collection (F Lydian is after all a mode of C.) Commented Jan 20, 2016 at 1:46
  • @jjmusicnotes I was in the middle of major edit. See if that address some of your concerns I barely scratched the surface of what I want to write. Also I always find Lydian always comes though more with the melody rather than progression so a different example may be needed.
    – Dom
    Commented Jan 20, 2016 at 1:49
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    @Dom TBH, I think it obscurs your original point rather than validating / supporting. Just because something looks a certain way doesn't mean it necessarily works that way. On paper, I could let your progression slide by in F major, but if I listened to it, I wouldn't feel right leaving it that way. Since music is ultimately a "heard", we must defer to our ears for guidance. Following paper-vacuum logic, you could argue that there aren't in fact any modes and none of it matters anyway; what's to stop you from analyzing it in G mixolydian or something else to justify your reasoning? Commented Jan 20, 2016 at 2:00
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    @RockinCowboy In Western Equal Temperament, there are 12 pitch classes. In strictly mono-tonal music, yes, there are 12 possible pitch-class-centers. Commented Jan 20, 2016 at 5:32
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    @ToddWilcox Absolutely not; my point was that just because you analyze a piece a certain way on paper using your eyes, doesn't mean that it actually sounds the way you've analyzed it. The whole point of analysis is to explain why music sounds the way it does, but too many people get caught up in what it looks like. This is dangerous because you're operating in a vacuum then, and you'll twist the music to justify your analysis. Much music has been written with no existing key or even pitch centers. We need to make sure the notation matches the music, not our personal goals. Commented Jan 20, 2016 at 5:35


My college music theory professor always explained it this way: Key only means tonal center. If you say it's in the key of C, then you have to specify whether the mode is C major, C minor, or some other mode. He would insist that there is no such thing as the "key of C major". The correct way to say that is this: the key is C, and the mode is major.

So in your example, the key is F and the mode is Lydian. The correct key signature for this mode is a clef with no flats and no sharps. My professor would never refer to this key signature as the "Key Signature of C" or the "Key Signature of A Minor" because he wanted to make clear the distinctions between the slightly ambiguous ways that these terms can be used.

  • So the notes that would be in the key of F change according to the mode? Not the same notes? I suppose that might be correct if you consider that the notes in the key of A in major mode are not the same notes in the key of A in minor mode. So each key could be comprised of at least 7 different sets of notes and the key signature for the key of F would be different depending on the mode? I think that is what you are saying and though it seems counterintuitive on it's face - I actually think I am inclined to agree with you. Commented Jan 20, 2016 at 3:58
  • I think you've got my intent. This is my old professor's way of impressing upon us the importance of recognizing the tonal center, and then understanding that a composer can build different scales and modes on that tonal center.
    – user1044
    Commented Jan 20, 2016 at 4:18
  • So there are really only 12 keys in western music and each of these has 7 or more modes? If each key was limited to only 7 modes that would be 84 possible key/mode combinations instead of the 24 commonly thought of - each having one of 15 different "key signatures"? It's an interesting but perhaps enlightening way to look at it. Commented Jan 20, 2016 at 4:30
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    Although Key only means tonal center would be neat, I'm not sure if it quite agrees with the way people actually use the term 'key' - people do talk about major and minor keys, i.e. saying that the keys themselves are major or minor. Commented Jan 20, 2016 at 8:05
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    If i'm in the middle of a jam session and I ask "what key are we playing in?" and the answer is just "Eb" with no "major", "minor", "lydian" or whatever after it, I still don't know what to play. From that point of view, I can't use such a simplistic definition of "key" as your college music theory professor. Add to that the fact that when I was growing up, always listening to the classical music station, when they announced what they had just played or were about to play, they usually ended with "in the key of <note> <scale>". So I'm programmed to think the center alone is not the key. Commented Jan 20, 2016 at 21:00

F lydian has the same key signature as C major (in other words it has the same notes, the same number of sharps and flats, in this case zero.)

It also has the same key signature as A minor.

However all three are different keys, because they have different tonal centres. A key is named after the note it tends to gravitate to.

A passage in A minor clearly sounds different to C major. And F lydian sounds different again.

Another way of looking at it is that F lydian gravitates towards F, but differs from F major in that has a B natural instead of a Bb (sharpened 4th.) But the previous way of looking at is to me more useful when it comes to drawing out a scale (I play guitar.)

You need to learn to think both in terms of relative keys (which have the same notes) and parallel keys (which have the same tonal centre.) It's true that relative keys can be difficult to distinguish and somewhat subjective: For certain pieces, one person might say it was in C major and another in F lydian (though there are others in which everyone would be unanimous that it was F lydian.) On the other hand, parallel keys, because they have different notes, are far more distinct: nobody is going to confuse F lydian and F minor.

Here are a couple of songs by Lou Reed. Both are based on an insanely simple chord progression, one with C - F and the other with C# -F# Decide for yourself if they are major or lydian. In my opinion, it is the pull towards F in these songs that prevents this very simple progression from being boring.

Walk on the Wild Side


  • I'm beginning to think a piece of music that establishes itself firmly in F Lydian would more likely be considered a mode in the key of F as opposed to the a mode of the key of C - even though all the notes are from the key of C major. Plus 1 for a very simple explanation of your point. Commented Jan 20, 2016 at 19:22
  • @RockinCowboy Thanks. I added a couple of examples. For me, Walk on the wild side is definitely F lydian, everything ends on an F. What do you think? BTW, any idea how to reduce those thumbnails to a reasonable size? I wasn't expecting to see them at all. Commented Jan 20, 2016 at 19:52
  • Thanks Steve - I will listen to your examples. I don't know how to reduce the size of the thumbnails - sorry. Commented Jan 20, 2016 at 20:26
  • I feel a pull back to C (C# in second example) on those songs. They seem to want to resolve back to C but I can see where there is some ambiguity there - like it could be either. Commented Jan 20, 2016 at 20:40
  • The fact that a piece of music has one flat in the key signature does not mean that the majority of B's are flatted, or even that any are flatted. There is a strong convention that pieces in major-ish modes should use the key signature of the associated Ionian mode, along with appropriate accidentals, and those in minor-ish modes should use the key signature of the associated Aeolian mode, likewise with accidentals.
    – supercat
    Commented Jan 5, 2018 at 0:44

Key signature and note collection notwithstanding, a musical composition that is written in F Lydian is NOT a mode of the key of C major - even though the key signature would be the same as for C major and all of the notes in F Lydian are also in C major.

In fact, the so called “key signature” does not always tell you what key a musical work is written in. And just because all of the notes in a composition can be found in the C major or A minor scale, the piece may not necessarily be in the key of C major or A minor.

To prove this, let’s look at the key of C major and A minor. I think it would be hard to argue that those two keys are the same. They are different keys altogether even though they share the exact same notes and the exact same key signature. The tonal center of A minor will be an A note and the tonal center of C major will be a C note.

It may also be helpful to consider that the key signature for C major is different than the key signature for C minor. Even though both keys share C as the tonal center – they have different notes and different key signatures.

Although the key signature will often provide a clue as to what key a musical work is written in, it is not the way to tell for sure. The key to determining the key (excuse the pun) is to find the “tonal center” of the composition. In other words, which note do the rest of the notes revolve around, start with, or want to resolve (gravitate) to. Often the best clue is in the harmony or chord progression which may lead you back to the tonal center.

The bottom line is each key has many different modes. You can refer to these modes based by the Greek names such as Lydian, Phrygian, Dorian and so on. Or you can say that it is major, natural minor, melodic minor or harmonic minor. C major, C natural minor, C harmonic minor and C melodic minor are all modes of the key of C because they all share the same tonal center - C. However they all have a different set of notes and a different key signature.

What determines the key of a piece is not the notes it contains or the key signature, but the note that establishes itself as the tonal center.

So F Lydian, despite having all the same notes as C major and sharing the same key signature as C major, is actually a mode of the key of F because F is the tonal center.

  • Looks good to me - the only thing I'm not quite sure about is that you've said that (a piece in) F Lydian is NOT a mode of the key of C major, but you've also said each key has many different modes. How are those statements consistent? Commented Jan 21, 2016 at 11:07
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    @topomorto F Lydian is a mode of F. It's not a mode of F major or C anything. C Lydian, C Dorian, C minor, C major are all modes of C. All twelve chromatic tones in the Western Music alphabet each can have many modes which can also be construed as different keys. Commented Jan 21, 2016 at 20:25
  • A lot of the confusion here is due to to the hegemony of "major" and "minor" as the only "godgiven" modes. F Lydian has the same tones as C major; but that doesn't mean it's somehow "defined by" or "subservient to" C major. Life is complex, and so is music. Commented May 5, 2018 at 16:57
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    @ScottWallace Complex indeed. Life and music. But I do believe music makes life more enjoyable. Don't you agree? Commented May 6, 2018 at 18:19
  • @RockinCowboy- c'mon, do you even have to ask? Without music I would curl up and die. Well, maybe not right away, but yeah: music does make life more enjoyable. Commented May 7, 2018 at 9:45

To me, "mode" is just a word we use instead of "scale" for certain scales. From that point of view, you might as well be asking me if "A minor actually belongs to the key of C major".

To me a key is both a scale and a tonal center. A different tonal center means a different key.

When you start a piece in A minor and modulate up to C major, you are now playing in a different key. From that point of view, F lydian and C major are two distinct keys that just happen to share the same notes (in equal temperment), the same way A minor and C major are different keys that share the same notes.

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    I did not think keys and modes were the same thing. But I could be wrong. Commented Jan 20, 2016 at 4:08
  • See my comment to Dom's answer. According to the idea that the tonal center defines the key, there can only be 12 possible keys in western music because the tonal center could only be ONE of the 12 possible notes (modulation notwithstanding). But if you take each of 12 possible tonal centers - and each can have 7 or more modes, would that not mean there are more than 12 key/mode combinations? Or are many of them redundant like the key of F# and Gb? The clearer things get the more confused I get. Commented Jan 20, 2016 at 4:40
  • In equal temperament F# and Gb are the same thing but that still leaves us with 12 possible tonal centers (7 white keys plus 5 black keys on the piano). Then there are seven modes so you could look at it as 84 different possible keys, except the seven modes are not the only possible scales. When you add in other kinds of scales and even possibly microtonality the number of potential keys becomes huge. This is assuming that by "key" we mean a tonal center and a scale pattern (or two or three, depending on what exactly you're doing). That's just one way to look at it but it works all right. Commented Jan 20, 2016 at 4:53
  • @RockinCowboy If you consider A minor and A major to be two different keys, then you are seeing the scale pattern as part of what makes a key. If you see A major and C major as two different keys, then you are seeing the tonal center as another part of what makes a key. You could take the view that a scale defines the chords used in a key, or instead that that chords that make up the tonality define a scale. Either way, you have a center and a pattern of chords/scales based around that center and that gives you a key. If the pattern is a "mode", it's still a pattern around a tonal center. Commented Jan 20, 2016 at 4:57
  • @ToddWilcox - in your second sentence, last comment, did you mean 'If you see A minor and C major...'?
    – Tim
    Commented Jan 20, 2016 at 7:44

Interesting question, Cowboy. From looking at sheet music for 'Scarborough Fair', which is Dorian mode, the convention seems to be to use the key signature of Em and to use an accidental to mark the c#.

I was taught in college that a 'key' is defined by the use of a dominant 7th chord. Minor dominants indicate a mode.

Interestingly, 'Walk on the Wild Side' sounds lydian to me, but uses a C major dominant, but C dominant 7 does not work.

I was taught the some music is ambiguous in that it is subject to more than one correct analysis. The point is to write stuff that people like. Have fun!! ;-)


let's simplify this and first answer a couple of basic questions about modes and modal music;

(1) All music is modal (2) A true mode (other than Maj./Ionian or natural minor/Aeolian ) are limited to 5 tones and only to 1 octave range, from the tonic to the dominant. In other words, 5 tones are not enough to establish either major nor minor tonality. (3) All modes (other than Ionian and Aeolian) have no definite key center, the modes can only tend towards major or minor characteristics, with the exception of Locrian- which has neither
maj. nor minor character, such as the diminished modes or all symmetrical scales for that matter. (4) The "key" / characteristic of a mode or modal piece is therefore noted by it's own unique modal name- regardless if it's built from the parent scale of C-major. In this case F Lydian belongs to the key of C-Maj., but only in the sense that it is built from and is the 4th of the 7 modes of the C Maj. scale but is not in the "key" of C- Major, it is in the mode of F Lydian, F being the tonic note (primary tone) that you would be resolving to- in addition to the 4th tone (the subdominant) being raised 1/2 step in comparison to the C major scale. (5) Diatonic Harmonic theory and analysis is not to be confused with modal Harmonic theory and analysis.

  • (2) - I thought the 3rd defined major or minor, as in Dorian and Phrygian as well as Aeolian would be construed to be minor. All 3 accepted minors have the same first five notes, so surely that's enough
    – Tim
    Commented Jan 20, 2016 at 12:44
  • " ...modes (other than Ionian and Aeolian) have no definite key center, the modes can only tend towards major or minor characteristics" So are you saying that a piece in F Lydian mode is not in ANY key? "... but is not in the "key" of C- Major, it is in the mode of F Lydian, F being the tonic note (primary tone) that you would be resolving to ..." - So if the song is in F Lydian mode is it in the key of F? Or just not in any key? Commented Jan 20, 2016 at 19:16
  • A true mode (other than Maj./Ionian or natural minor/Aeolian ) are limited to 5 tones - can you clarify what you mean? Commented Jan 21, 2016 at 0:53
  • Answer to Q.-Nr.2 (Rockin Cowboy): The modes do not have a "Key" signature, that is why it is called a "mode" and not a "key"- if you want to think in terms of "keys" it would be in the key of F Lydian- although there is no actual key center for any of the modes, there is only a tonic (main note) in a mode that one can resolve back to. So, the answer is that there is no key, there is only a reference note that signifies which note the mode will be encompassing. Commented Jan 21, 2016 at 13:11
  • Answer to Q.-Nr.3(topo morto): Yes, a true mode (as defined in music theory, ref: Harvard Music Dictionary-etc., also as defined in general) consists only of the tonic to the dominant intervals (1-5) of the normal diatonic (7 tone) scale. In a sense it is only a large fragment of a normal diatonic (aka: heptatonic) scale, not to be confused with a pentatonic scale or the pentatonic modes. Commented Jan 21, 2016 at 13:12


According to the above website there are only 24 keys in music, 12 major and 12 minor. Therefore, technically, F Lydian is in the key C major, with F as the tonal centre. I get a sense that a key here is referred to a as collection of notes available (except accidentals) to build harmony and melody. I think this makes sense. Essentially, it's just a label, as long as we understand the crux of it here is no point splitting hairs!

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