Wednesday, January 26, 2011

Major and Minor Interval

Interval is the distance between two notes. In a scale, interval is measured from the root note. The root note is counted as 1.

For example, in C Major:
C-C
C-D = Major Second
C-E = Major Third
C-F = Perfect Forth
C-G = Perfect Fifth
C-A = Major Sixth
C-B = Major Seventh
C-C = Perfect Octave

For C Minor:
C-D = Major Second
C-Eb = Minor Third
C-F = Perfect Forth
C-G = Perfect Fifth
C-Ab = Minor Sixth
C-Bb = Minor Seventh
C-C = Perfect Octave

Major interval can only be used for the 2/3/6/7 notes in Major scale

Minor interval can only be used for the 3/6/7 notes in Minor scale. Minor interval is always half step shorter than the major interval of the same name.

Pythagoras, born circa 580 BC, initiated the idea that if a vibrating string is divided in half, it produces the octave above the open vibrating string.  In other words, the ratio of the fundamental string to to the divided string is 1:2 will create a octave interval.

Perfect intervals (unison, forth, fifth and octave) is perfect because they are produced from perfect or pure frequency ratio.  For fifth, the ration is 2:3 and for forth is 3:4

Identifying Key

The key signature does not differentiate Major or Minor key. 99.99999% of time, Minor key seldom appears in its natural form. Usually the melodic or harmonic minor keys are used in music. And both forms contain a leading note (raised 7th). Major key does not need to do so because the 7th note is already raised.  So if you found one note is sharped frequently and that is the leading note of the related minor key, the piece is likely in the minor key.

For example, if to know if the piece is A minor, look for appearance of G# in the piece.

Monday, January 24, 2011

Scale

(1) Pentatonic scale comprises 5 notes (1, 2, 3, 5 6) which simple fractional relationship with each other in term of frequency.

1, 1+1/8, 1+1/4, 1+1/2, 1+2/3, 2 or
1, 1+1/8, 1+2/8, 1+4/8, 1+6/9, 2

There is no semitones within the pentatonic scale that make the notes sound good together.  The scale has the following interval pattern:

1 1+1/8 1+1/4 1+1/2 1+2/3 2

The interval between the third and forth notes is more than 1 tone.  Likewise between the fifth and the next octave note.

(2) Major scale is built from the pentatonic scale plus two notes.  Two note was added in the interval higher than 1 tone - sub-dominant and the leading note.  The pentatonic notes have the follow relative frequency to the tonic:

The two additional notes are 1+1/3 (which is 1 semitone above 1+1/4) and 1+7/8 which is 1 tone above 1+2/3 and 1 semitone below 2 (octave).

1, 1+1/8, 1+1/4, 1+1/3, 1+1/2, 1+2/3, 1+7/8. 2

Major scale has the following interval pattern:

WWHWWWH

A drawback of the major scale is the tendency towards definite, complete statements.

(3) Minor scale has less definite full stops. Minor scale takes the same set of note as a major scale but use a different tone as the root.  For example, C manor and A minor uses the same set of note but the root (tonic) is C and A respectively.

There are 3 different forms of minor scale. 

Natural minor scale has the following interval pattern:
WHWWHWW

Comparing to the major scale, 3 notes (including the leading note) move down 1 semitone.
Comparing C Major to C Minor, the 3, 6 and 7 notes (E A B) are flat in C Minor.

C, D, E, F, G, A, B, C
C, D, E, F, G, A, B, C

The relative frequency is:

1, 1+1/8, 1+1/5, 1+1/3, 1+1/2, 1+3/5, 1+3/4, 2

Natural minor lacks the leading note.  So it does not sound good when the melody going up as the seventh and the octave note is too far apart.  It sounds good for melody travelling down in pitch (descending melodic minor).

For the ascending melodic minor, 2 of the notes are re-instate to their major positions.  The leading note is restored and its neigbouring note also to smoothing out the big gap.  The sixth note also bumped up a semitone so that it does not sound too far apart from the leading note too.

Ascending melodic minor scale has the following interval pattern:

WHWWWWH

C, D, E, F, G, A, B, C
C, D, E, F, G, A, B, C

The relative frequency of ascending melodic minor are

1, 1+1/8, 1+1/5, 1+1/3, 1+1/2, 1+2/3, 1+7/8, 2

For composing melody, we use the natural minor for the part going down and melodic for the part that going up.  However, the two minor scales pose a problem for creating chord which sounds good for both directions.  The harmonic minor is a compromise by only restoring the leading note from the natural minor.

WHWWHW#H

The 6 and 7 note is now 1.5 notes apart.   This creates a melodic awkward.

Classical musician practice minor scales by playing melodic minor as the scale ascend and natural minor in descend.  Harmonic minor scale is rarely practised.  This is more a harmonic tool and not a melodic one.

Wednesday, January 12, 2011

Key Signature

The sharp and flat have fixed position and sequence in key signatures.

#: Father Charles Goes Down And Ends Battle
b: Battle Ends And Down Goes Charles's Father

Sharp Key Trick - For keys that have sharp, find the last sharp and go one note higher. If the note is sharped in the key signature, the key is sharped.

For example, for A Major, there are 3 sharps. The last one is G. So the key is A Major. For F# major with 6 sharp, the last sharp is on E. since note F is sharped, the key is F# Major.

Flat Key Trick - Find the second last flat (from the right). The name of the flat note is the name of the key. Similarly, if the note is flatted in the key signature, the key is flatted.

For example, Ab Major with 4 flat, the last flat is D and the second last flat is A. As note A is flatted in the key signature, the key is Ab major