How the Key Signature Denotes the Mode

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Big Bad Bill
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I just downloaded the TAB for Petrucci's 'Glasgow Kiss' and above the key signature it says 'Key Signature denotes E Mixolydian'. How and why can it give you this information? The key signature is A and the piece starts with an E note which is the fifth note of the A major scale. Is is simply because of this? If it started with a D would the signature denote D Lydian?
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b2
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E mixolydian and A Ionian share the same key signature.

From another website:
- "When two modes share a key signature, we say they are related.
(You may have heard of relative minors; well, relative modes is the
same idea.) "

So really you cant say if it is E mixolydian or A Ionian. It could be both.
But I guess they write 'Key Signature denotes E Mixolydian' to let you
know that the song is in key E and not A.

The first note of the song dont tell you anything at all, only that it is the
first note :wink:

The key siganture is just to help you a little. But it will not give you
all information.
nouromenon
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Yup, it usaully means that even though the chords and notes are all from A major, the focus is on the E major chord (mixolydian mode) as the most important / home chord in the progression as opposed to the A major chord being the (I) chord, same with all modes. Just as F# minor chord of the same key would be the (I) chord for the Aeolian mode (or relative minor), yet still all chords and notes would still be from A major.
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Ricardo
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'Key Signature denotes E Mixolydian'
They did not really need to write this. The key sig just tells you the number of sharps or flats that occur most often in the piece coming up. The music itself reveals the tonality or key. Sort of like you are painting a picture of a forrest, but you use green paper instead of white so you don't have to color in all the leaves.

Not to open up more modal arguements, but some folks view "modes" as either major or minor, and actually write using a key sig for parallel major or minor, depending on the mode. For example, E mixo could be written w/ 4 sharps in the key sig, but the author will write in D natural as an accidental EVERYTIME it occurs. The idea is to force the reader into accepting E as tonic, always with flat 7 though. E dorian might be written w/ one sharp in the key sig, but the note C# will always be an accidental.

So whoever made the transcription was just taking care to spell it out that the tune was in E, mixolydian mode specifically, but was saving ink by using the key sig for A major.

Ricardo
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Ricardo's got it down pretty well. I try to avoid using accidentals because it makes sight reading a bit more difficult (for me at least :p)
markelia
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Big Bad Bill wrote: I just downloaded the TAB for Petrucci's 'Glasgow Kiss' and above the key signature it says 'Key Signature denotes E Mixolydian'. How and why can it give you this information?
Traditionally, key signatures generally only indicate western music's major and minor tonalities. Key signatures do not give you information on what "mode" a song is in. A key signature of 2 flats tells you that your tune is probably in Bb major, or its relative minor, G minor. You determine whether the song is in Bb major or G minor by paying attention to the tone or triad of rest and repose which provides resolution in the context of the tune. This holds true for modes, also. If the key signature shows 2 flats, but the song seems to "resolve" to C minor via a boogie progession like C minor, Eb major, F major, C minor, then the tune is modal (C dorian).

If I had never heard the Glasgow Kiss tune and I started to read the music (assuming the E mixo comment in the manuscript was deleted), my first impression would be that the tune has 3 sharps and is in either A major or F# minor. After playing a bit of the tune, it would occur to me that the tune is not resolving to A major, but rather to E major. This would make a lightbulb go off in my head (aha! E mixo).

Big Bad Bill wrote: The key signature is A and the piece starts with an E note which is the fifth note of the A major scale. Is is simply because of this? If it started with a D would the signature denote D Lydian?
No. The first or last notes/triad do not define the mode/tonality or tone of rest and repose. You determine the place of rest by playing or examining the music.
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Big Bad Bill
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These are all very helpful comments, chaps-thanks! It seems the only way of telling the modality of a piece is to listen to it! But is this the case for major or minor pieces. I'm sure that my old theory teacher would look at a score and say, "By the number of accidentals I can see this is in the realitive minor of the key signature" or words to that effect. Is this the case?
Luan
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b2 wrote:E mixolydian and A Ionian share the same key signature.
The first note of the song dont tell you anything at all, only that it is the
first note :wink:
Right, but the last note can help to know the key.
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b2
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Sometimes the last note is the key but this is no safe rule.
Generally there are no safe rules, use your ears and knowledge.

Also the key signature only applies to the notes not the chords names
typically written above the staff.
The chords could be whatever but usually they are also from the same
key and scale.
Luan
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b2 wrote:Sometimes the last note is the key but this is no safe rule.
Generally there are no safe rules, use your ears and knowledge.

Also the key signature only applies to the notes not the chords names
typically written above the staff.
The chords could be whatever but usually they are also from the same
key and scale.
Yes, for example For the Love of God

The second chord is an F when the song is in E minor.

What I don't know is what chord are able to use, out out of the E minor scale.
thelordofcheesecake
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Luan wrote:Yes, for example For the Love of God

The second chord is an F when the song is in E minor.

What I don't know is what chord are able to use, out out of the E minor scale.
When I play "For The Love Of God", I switch between the E natural minor shape 7th position, to the F lydian shape 8th position, which you play over the Fmaj7#11 chord in FTLOG. It's a close key modulation, with one note of the E minor scale changed (i.e. F# to F), so you can't really use the same scale over it.
jmchambers5
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The first and the last note aren't sure ways to find a key sig, but if i'm analyzing something with one sharp in the key sig and it starts and ends on a G chord with a G in the melody, I'm going to assume it's in G until I hear otherwise.
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