This would avoid the confusion to some, of saying that the key/mode of A dorian has a key signature of G. I’m all for making things clearer for people learning music. If a piece is in D dorian, I always put “D dorian” above the key signature of C. This makes it clear what mode/key the piece is really in.

I’ve read your replies, thanks for the comments and answers. I realised I was being provocative in suggesting a name change to a term that is firmly entrenched in our culture, and also calling a mode a key . But I was hoping to find some way of creating a disconnect between “key Signature” and the tonal centre of a piece of music.

If the key signature is misleading, it helps if the tonal centre or mode is notated. Recently, I was given a simple 17th century Playford dance piece with a key signature of G. But the use of C#, and the chord structure, made it clear it was in the key of D major, as annotated by the person giving me the music. However, if I was creating a walking bass line around a diminished chord in jazz, it wouldn’t help annotating it as a super locrian mode. I just have to know that half-whole tone intervals are used.

The discussion Key signature for writing in modes other than major and minor confirms my belief that the key signature just tells us the notes being commonly used, and any mode/tonal centre should be annotated. And sometimes using the “wrong” key signature, with more accidentals, helps people understand where the tonal centre may lie. E.g, using the key signature of F for a piece in D dorian.

This extract from the discussion quoted just above, sums it up nicely for me: 'The term "key signature" used in English does not translate exactly the meaning of what it is. In all other languagues, the literal translation would be "clef armature". So a clef armature is not meant to represent a musical key, but to simplify the process of reading music.' Thanks Flávio.


3 Answers 3


A scale is a set of notes. That may be a major scale, any one of several minors, and possibly modes.

A key signature merely gives which notes in a piece are likely to be included in the following piece. The 'key signature* of 3# gives us a clue that the piece could be in A major, or maybe F#m. If it is indeed in F#m, then there are often several note changes that need to be made along the way, as harmonic minor has a slightly different set of notes in its scale from melodic (including possible natural minor).

So, even when the 'key sig.' is 3#, it's often not reflecting what's likely to be going on. We have to look for clues - the last note, is it A or F#? Is there a change in what the leading note's called? What harmonies are most prevalent?

That's the same with modes, the method you describe being my preferred, although if the 'key sig.' was 3#, I'd expect a B at the end, and a minor tonality to the piece if it was in B Dorian.

So, even with a change of name to 'scale signature', I don't see how that would help a lot. At least one composer, Bartok, I think, used something like Bb and F# in the 'key sig.' to indicate G minor - which actually makes some sense, however, it obviously didn't catch on - otherwise we'd be using it now!

  • 1
    Bartok often writes stuff on the edge of not being in any fixed mode; hence the wacky key signatures. Commented Oct 29, 2018 at 12:43
  • @CarlWitthoft - fair comment, but actually, with a key sig. of Bb and F#, it gets pretty close to being more accurate than Bb and Eb. Maybe he included Eb as well, not sure!
    – Tim
    Commented Oct 29, 2018 at 12:45

Let's take a step back and look at what a key is first. A key is a very specific concept in music theory. The key tells you what the tonic of a pieces is and the general type of Harmony to expect. A key will never indicated what scales to use which especially in a minor key could look vastly different from the key signature assigned to the key.

Since tonal harmony focuses on major and minor, trying to indicate modes with a key signature is always difficult. Most people just use if the mode is major or minor to determine what key signature they should use. For D Dorian, since it is a minor mode you could use the key signature for D minor to indicate it. Not a perfect fit, but it still preserves the indication on the tonic.

  • What is a key in the first paragraph? Are you explaining what the key signature is, or are you defining the word key? In either case, the connection between key and key signature is not very clear by reading the first paragraph.
    – JiK
    Commented Oct 29, 2018 at 19:31
  • @JiK I cleaned it up a bit hopefully. Key and key signature are related topics since a key signature points to a key so explaining what keys are was needed at least for the question in the title.
    – Dom
    Commented Oct 29, 2018 at 19:44
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    That still doesn't seem clear. An example would help. In a piece in E minor, is the key "E" or "E minor" or "G" or something else, and is the key signature "E minor", "G major" or "one sharp" or something else?
    – JiK
    Commented Oct 29, 2018 at 20:15
  • Or maybe a better example would be a piece in another mode. The reason I'm saying this is that the question talks about "D dorian" as a key, but a comment says that D dorian is not a key. This answer starts by "let's look at what a key is first" but doesn't actually give enough information to answer that question.
    – JiK
    Commented Oct 29, 2018 at 20:27
  • 1
    @Dom But given your answer leans heavily on "what is a key", (and given the asker's confusion with respect to key vs. scale vs. mode) it's probably worth attempting to clear up confusion on what, exactly, a key is. - You don't necessarily need to repeat details here, but I'd suggest picking one of the existing answers on this site which makes the point you want to make in the context of this answer, and then link to them.
    – R.M.
    Commented Oct 29, 2018 at 20:58

The key signature only tells you the number of accidentals used for the basic tonality.

From that starting point we can see that we don't know the tonic merely from a key signature, therefore we don't know what key/mode/scale will be used.

For example, if the key signature is one sharp. We could have a key of G major... or it could be E minor. Also, it could indicate a number of modes: C lydian, A dorian, D mixolydian, etc.

You must look at the score to really know what the tonic and mode are. Typically you can tell that by looking at the beginning and ending of the piece where traditionally the music starts and (especially) ends on the tonic.

You could think of the key/mode as an indicator of a scale. But that might be misleading when there are chromatic inflections of a basic diatonic scale such as chromatic passing tones or the raised ^6 or ^7 degrees in a minor key.

Just an historical aside: the modern key signature for minor keys indicates a "lowering" of the ^3, ^6, and ^7 scale degrees. So Eb, Ab, and Bb for C minor. But in Bach's time the key signature lowered only the ^3 and ^7. So back then Ed and Bb were the key signature for C minor. If we are looking for a scale, it sort of looks like a dorian mode signature, but that would be wrong. The music would be minor key using natural, harmonic and melodic minor scales.

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