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Determining Key Signature

Posted by inkd 
Determining Key Signature
December 28, 2010 07:08PM
Hey, guys. I am wondering how I am to go about determining a key signature. I have attached a photo of an example melody for which I would like to determine the key. I have referred to the circle of fifths, and, taking into account the flats used (D & G), I guessed that my key was either D Flat Major or b flat minor. Firstly, how do I go about figuring this out? Do I look at the sharps/flats used in the measure and determine it based on this, or is there some other method? Secondly, how am I to tell whether or not it is major or minor (as in D Flat Major and b flat minor)? Thanks for the help!

Here's the melody:
Example Melody
Re: Determining Key Signature
December 28, 2010 07:39PM
That short example has been wrongly notated. The Db is actually C# and the Gb is F#. So there are 2 sharps, no flats. If those are the only 2 sharps in the whole piece or section and there's no F or C naturals and no flats further along the line somewhere (you've only given a couple of bars) then it's most likely in the key of 2 sharps, i.e., D major or B minor. The melodic phrase based around D - C# suggests that it's D major rather B minor.
Re: Determining Key Signature
December 28, 2010 09:50PM
Thank you for the timely response. Could you explain to me why those would be sharps and not flats? Also, do I look at the piece as a whole and then determine the key signature, or is it best to do it staff by staff? Another point of inquiry, I've been told that concluding whether it is major or minor is dependent upon the note on which it resolves. Could you better explain this to me? Again, thank you for your help!
Re: Determining Key Signature
December 28, 2010 10:35PM
inkd Wrote:
-------------------------------------------------------
> Thank you for the timely response. Could you
> explain to me why those would be sharps and not
> flats? Also, do I look at the piece as a whole and
> then determine the key signature, or is it best to
> do it staff by staff? Another point of inquiry,
> I've been told that concluding whether it is major
> or minor is dependent upon the note on which it
> resolves. Could you better explain this to me?
> Again, thank you for your help!

Mainly it's because of the D natural being there. If this had been in the key of Db as you thought, then the presence of D natural in such a prominent position and repeated even more than than the Db would be strange and very unlikely. If you play it, you can hear how the D natural is important, much more so than the Db which is just a decorative 'neighbour tone'. So, from the perspective of D being the important note, that neighbour tone, a semitone below, is called C# as C# belongs to the key of D, but Db doesn't.
Also, you can hear how the melody is outlining a D major chord by going to the chord's 3rd. The 3rd of D major is F#, not Gb.

Yes, the note of resolution determines the tonal centre and the key in most cases.The note of resolution means the note that, when we hear it, (in a suitable context) gives us a sense of completeness or 'coming home'. In the short example given, there is no real resolution to tell us 100% what the tonal centre is, but given what we've got D is the most likely.
Another sign post to help you determine whether a key is major or its relative minor is that if it were in the relative minor key we should also expect to see the 7th scale note being raised at times within the music as an accidental (rather than in the key signature). This is because minor keys commonly have their 7th note raised in order to lead to the 'tonic' (note of resolution) more convincingly. The harmonic minor scale is the minor scale that reflects that common practice.

In your example, that raised 7th note would be A#, leading to B, but the example isn't long enough. If there are A sharps leading to B later on then it would point to the key of B minor rather than D major.
Re: Determining Key Signature
December 28, 2010 11:06PM
My, that's quite a load. From this post it seems that there is no hard-set, formulaic way to determine the key signature/key of a song. I see I have some brushing up to do. >:D< In any case, thank you for the help. Once I have finished the piece, or at least developed it a bit past its current point, I will likely revisit this issue. Thank you!
Re: Determining Key Signature
December 29, 2010 08:23AM
inkd Wrote:
-------------------------------------------------------
> My, that's quite a load. From this post it seems
> that there is no hard-set, formulaic way to
> determine the key signature/key of a song.

Yes there is.

Firstly, write out all the notes, and try to exclude repetitions of the same letter (eg flat or sharp and natural versions of the same note).
Major keys always have either all sharps or all flats, but most importantly you need one of each letter and only one.
Occasionally a tune will have "chromatic" notes (from outside the key), and these will inevitably be different versions of one of the key scale notes. But the clue to these is they will be very rare - if you're left with two versions of one note letter, whatever you do, assume the rarer of the pair is the chromatic note and the other the key scale (diatonic) note.

Secondly - and perhaps most importantly! - play the music. Which note sounds like the tonal centre of the tune? Which note does it end on, or sound like it ought to end on? That's the keynote.
If that's accompanied by a major chord, then the key is major; minor chord and the key is minor. This is regardless of what other notes or chords the tune may contain: you should expect the other notes and chords to support your aural conclusion, but there will commonly be exceptions.
Eg, in rock, it's very common to "borrow" chords from the parallel key. Eg, a song in E major might have a few notes or chords taken from E minor. But if the tonic chord is E major, then the key sig should have 4 sharps - even if some of them are turned into naturals throughout the piece.

> Once I have finished the
> piece, or at least developed it a bit past its
> current point, I will likely revisit this issue.#

You're welcome!


BTW, on your specific clip, Fretsource is probably right that your key is D major. But those 3 pitches could also be part of A major, or the relative minors of either key B minor or F# minor. There's a very slight possibility that such a passage could occur in other keys, but at least one of the notes would be chromatic.
D major or B minor are still the most likely answers, given those 3 notes. Both have the same key sig - but are not the same key! (This is where keynote and listening matters. If you're starting and - especially - ending on a Bm chord, your key is B minor. If D is your "home" chord, then D major is the key.)
IOW, you - we - would need more information to be sure of the actual key of your piece. But the rules for deciding are pretty simple.
Re: Determining Key Signature
December 29, 2010 09:44AM
Another thing to watch out for is that temporary key changes may occur within a piece of music, but the key signature usually won't be changed to show the new key. Instead, the new key is shown by accidentals specifying notes foreign to the original key. This highlights the point that Jon and I both made earlier, which is that the best piece of equipment you have for this is your ear. If you can hear and recognise that note/chord of resolution, then you have the key at that point and everything else is academic.

BTW, incorrect sharp/flat notation is a common problem when you enter notes from a keyboard into notation software but don't tell it the key signature to begin with. Most software doesn't assume there is no key signature. Rather, it assumes the 'neutral' key signature of no sharps or flats. In other words, it thinks the key is C major or A minor. I'm assuming from the neat looking printout of your example that that's what you've done in this case.
So the first note is D, which is fine The next note, a semitone lower, is foreign to the keys of C and A minor, so the software just chromatically alters it from D to Db. If it had known that you're actually in the key of D or Bm (or A or F#m as Jon pointed out) then that note would automatically be correctly notated as C#, and the Gb as F#.
Re: Determining Key Signature
December 29, 2010 10:09PM
@JonR: Great information! Thanks! Once I'm back in class, I'll most likely find our music theory teacher and ask her to go more in-depth on this topic. We've been meaning to set aside a day for private study for sometime, now.

@Fretsource: Haha, you're exactly right. I didn't want to put in a key signature because I, of course, didn't want it to be incorrect. Thanks for the tips, man!

You two have been wonderful. Thanks for the advice, and I'll be sure to look more into listening for its "tonal centre". Have a good one and Happy New Year!
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