Let's say a key signature has one flat, B flat. It could obviously be F major, but it could also be in its relative minor, D minor. I already realize you could tell the difference with the tonic, what chords it uses, etc. but none of those methods are foolproof.

So is there any way one can be absolutely, 100% certain a piece is in the major key rather than the minor key?

ETA: I understand there are similar questions already asked, but there has been no satisfactory answer (they were either too specific or no answer was given).

  • 2
    To get perspective, in what kind of situation do you have to do such classifications? I suppose something really bad will happen if someone disagrees with the opinion about the key? Sep 21, 2019 at 7:10
  • @piiperi is right, in that if you are talking about natural minor, it truly doesn't matter. If the case is melodic or harmonic minor, it's pretty obvious if it's in minor because of the accidentals used. Overall, it seems like a very strange question to me. I frequently compose pieces where 1+ instrument(s) play(s) in X major and the other 1+ instrument(s) play(s) in relative or parallel minor (or both).
    – Pyromonk
    Sep 21, 2019 at 22:47
  • If I am going to talk to someone about a specific piece, let's say a waltz, I'd want to say something like "Waltz in [key signature]" and not make a fool out of myself.
    – Annie
    Sep 22, 2019 at 2:59
  • Why would you want to fool someone to believe you could feel the key even if you can't? Saying that the key feels ambiguous or changing is a valid statement just as well. If you say "waltz in some-key", then you claim that the key is unambiguous. How can you be 100% sure of that? IMO the key is something you feel. It's like telling if someone is happy or angry or something. If you can't tell a person's mood, then you'll have to admit you can't tell. Music is so much better if people don't have to prove their competence all the time. If you can't feel it, you can't feel it. Sep 22, 2019 at 15:19

5 Answers 5


The tonic of a given key is the note/chord which feels most 'at home'. The place where the piece is at rest, or could stop at that point, and no-one would feel it had to continue to be completed.

As ggcg states, minor keys usually have more accidentals, particularly the leading note, which doesn't show in the key signature, so needs taking up a semitone. Key sig. of Dm is B♭ - we don't put C♯ there as well, even though it gets used frequently in Dm!

Music being what it is, it makes its journey through relative major and minor keys when it feels like,(simple modulation), so sometimes there's no convincing proof as to which key it's in. 'Fly me to the Moon' starts on A minor, but ends on relative major,(C), so what key do we put it into? So, whilst there is a possibility with a lot of pieces, it's not an absolute.


In the realm of 1950s ABRSM theory exams, we were taught to spot the sharpened 7th note (which would be notated as an accidental) as the invariable clue that it was a minor key. The harmonic minor scale was seen as the 'normal' version. Melodic minor was a slightly disreputable alternative, Natural minor wasn't even mentioned. We were also warned to look out for the 'tierce de Picardie' where a minor key piece might be given a major final chord.

Real-life music, even in 1950, was more complicated of course! Even simple tonal pieces might move freely between major and minor. Sometimes there's no right answer to 'is this piece in C major or A minor'. I'm afraid your urge towards neat classification may have to go unfulfilled.

  • There are lot's of pop songs in the 70ies and 80ies Am-F-G-Em. Would you agree they are neither major or minor but in one of the modes as Aeolian or Phrygian? Sep 21, 2019 at 12:03
  • @AlbrechtHügli - I'd only agree if all the notes fit in the Aeolian or Phrygian mode. Too often in similar music, not all the notes do, so I classify the piece in major or minor as necessary based on the tonic (or most commonly used chord).
    – Dekkadeci
    Sep 21, 2019 at 12:22
  • May Aeolian or Phrygian songs not have chromatic notes?
    – Laurence
    Sep 21, 2019 at 17:23
  • @Dekkadeci - Devil's advocate! 'If all the notes fit... We don't use that criterion to determine major or minor keys. In key C, for instance, there may be a momentary modulation which involves an F#. That doesn't stop us saying it's 'in C'. So why not use the same 'rule' for Dorian, etc?
    – Tim
    Sep 22, 2019 at 6:51
  • There may also be an F# (or a C#, or an Ab...) that DOESN'T imply a momentary modulation at all.
    – Laurence
    Sep 22, 2019 at 11:10

Actually if the tune is in the relative minor key it will likely have more accidentals as it would use harmonic or melodic minor, e.g. modes with a raised 7th (leading tone) and possibly raised 6th. The major key would not typically employ these notes.

This is not a guarantee as many modern songs in minor keys use natural minor. How you can tell is based on the structure of the melody. The melodic themes would emphasize the {1, b3, and 5, possibly b7} of the rel minor scale on strong beats. In other words if melodic ideas gravitate to notes of the vii chord or begin and/or end on the vii then it will have that minor sound and feel.

However, there are exceptions. The fact is that one can take a song completely in a Major key and via chord subs harmonize it in the relative minor (and vice verse) and it will work! It will sound good. In such cases the key may be ambiguous. There are lots of ways to play this trick on the ear so in a sense there may be no foolproof method.

Also keep in mind it is not uncommon for songs to change key so one cane modulate between X major and its relative minor.


Is there any way one can be absolutely, 100% certain a piece is in the major key rather than the minor key?

In general, no. Perception of tonality is subjective, and saying that a piece is in a given key isn't an objective statement of fact about the piece - it's more like an invitation to hear the piece from that perspective.

You can imagine cases where it would be very hard to argue that a piece was in D minor rather than F major - for example, if there was never a D minor chord or an D note played! but even then, someone might still consider the piece to be in some other mode of F major.

I guess if the composer has written "F major" on the score, that might give you an 'official' answer in some cases...

  • 2
    Now I want to find a piece with a single flat in its key signature but no D.
    – badjohn
    Sep 21, 2019 at 7:38
  • @badjohn - Easy: the "Engine Engine Number 9" children's rhyme song. (OK, the F major version basically consists of only A's and C's, at least from the clarinet book I recall.)
    – Dekkadeci
    Sep 21, 2019 at 12:27
  • 3
    @Dekkadeci Oh yes. I should have thought of beginner's exercises. I think that my son's first violin book had a piece with just one note. Very hard to say whether it was major or minor.
    – badjohn
    Sep 21, 2019 at 12:33

You are talking about a piece of music - not only a short motif (like the beginning of Beethovens' fifth symphony) ...

I pretend that it is absolutely certain to derive this from the sharps (leading tone) or melodic lines or a second voice and especially from the "home tone" which is usually the finalis - except the piece "modulates" to the dominant like BWV 999 or ends in a chord with a major third (called Phrygian ending).

If you doubt about this you should give an example where you mean that there is an ambivalence.

  • 1
    Your 'Phrygian ending' is in fact the Picardy third (tierce de Picardie) !!
    – Tim
    Sep 22, 2019 at 15:17

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