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Welcome to your musical language lessons
My name is Eilish San and today I'm going to give you
some tricks to quickly identify
through the key signature in what key is
a score or how to write a key signature
for a given key
For this we are going to see what is known
as the circle of fifths
But what is a fifth?
A fifth is the fifth note of a scale
That is, if we are on the C major scale,
the scale notes are C, D, E, F, G, A, B, C
The first C is the first, D is the second,
E is the third, F is the fourth, G is the fifth,
A is the sixth, B is the seventh
and the second C is the eighth
That's why it's called making an octave leap
or transposing an octave to change
from a C to a higher pitched C
In this case we are interested in the fifths,
and the fifth of C is G
The G major scale is G, A, B, C, D, E, F sharp, G,
so the fifth of G is D
Successively, the fifth of D is A,
its fifth is E, its fifth is B,
its fifth is F sharp or G flat,
its fifth is D flat, its fifth is A flat,
its fifth is E flat, its fifth is B flat,
its fifth is F and finally the fifth of F again is C
If we compare it with the possible key signatures,
we see that, starting from C major,
which is the key signature without accidentals,
each fifth adds a sharp to the key signature
C without accidentals, G with a sharp,
D with two sharps, A with three, E with four,
B with five and F with six sharps
As we saw in a previous video,
the key signatures with six accidentals are equivalent,
that is, the key signature with six sharps
and the one with six flats gives the same key,
being F sharp or G flat
From here, every fifth decreases
a flat in the key signature
G flat with six flats, D flat with five flats,
A flat with four, E flat with three,
B flat with two, F with only one flat
and back to C, closing the circle
In the same way we can refer
to the circle of fifths for minor scales,
starting from the equivalent minor scale
to C major, that is A minor
The fifth of A minor is E minor,
its fifth is B minor, then
F sharp minor, C sharp minor,
G sharp minor, D sharp minor
or E flat minor, B flat minor,
F minor, C minor, G minor,
D minor and back to A minor
Starting from a key signature without accidentals
in A minor we increase the sharps
until we reach the six sharps in D sharp minor,
that is, E flat minor with six flats in the key signature,
and we diminish flats from here until returning
to A minor without accidentals
In addition this circle can be read in reverse
What note has as its fifth a specific note?
We return to the example of C major,
the fifth of C major is G
The G major scale is
G, A, B, C, D, E, F sharp, G
C is the fourth of G major,
and in any major scale you can do the same
since all major scales
have the same structure of
tone-tone-semitone-tone-tone-tone-semitone
In fact it is this structure of tones and semitones
that gives name to the different scales,
all the minor scales will have another
structure equal for all of them,
all minor harmonic scales
will have another structure different from those of
majors and minors, but equal for all
minor harmonics, etc.
Therefore, the note that has as fifth
a given note, is its fourth
Thus, the circle read in reverse
is read as a circle of fourths
In this case, by jumping from fourth to fourth
C major, F, B flat, E flat,
A flat, D flat, G flat, the flats
of the key signature increase one by one
At this point we are
in F sharp major and if we continue
to jump from fourth to fourth
B, E, A, D, G, C,
the sharps decrease
from the key signature one by one
In fact, it is this same succession of fifths
C, G, D, A, E, B, F
the succession of sharps and flats
in the key signature, starting from F
The key signature of G major, with a sharp,
the sharp note is F
In D major, with two sharps,
the new sharp note is C
With three sharps,
the new sharp note is G,
with four D, with five A and with six E
If you used a seven sharps key signature,
the last one would be B
Again in a seven flats key signature,
the last flat would be F
With six flats, the last one is C,
with five G, with four D, with three A,
with two E and wit only one flat,
this is on the note B
And how do we know what key we are in
with the key signature, without having to think
about the circle of fifths or fourths continuously?
There is one last trick for this,
even easier than all of above
if you have a key signature without accidentals,
its obvious that it is a C major
if you have a key signature of sharps,
the major key of the composition is a semitone
higher than the last sharp of the key signature
That is, if there are three sharps
the last sharp is a G sharp,
so the key is A major
If there are six sharps, the last one is E sharp,
so the key is F sharp major,
since E sharp is actually F
If you are reading a score
with a key signature of flats,
the major key is the same as the penultimate flat
For example, if the key signature has two flats,
these are B flat and E flat,
so the key is B flat major
With four flats, the last two are
A flat and D flat,
so the key is A flat major
Be careful when there is only a flat
as you will not be able to use this trick,
in that case it is F major
So far everything related to
how to make a quick reading
of the key of a composition from the key signature,
or how to write the key signature
from the key of a composition,
any doubt or thing that you want to share
remember to leave it in the comments
I hope that you like this video, that you find it useful and I'll see you in the next video