Hi I am doing grade 8 theory (Trinity).
I need a quick and easy way to remember/ know of how to build blues scales.
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Take a natural minor, remove the 2nd and 6th degrees.
Add a sharpened 4th.
1 - b3 - 4 - #4 - 5 - b7
Tonic - Flattened Mediant - Sundominant - Sharpened Subdominant - Dominant - Flattened Leading Tone.
In terms of degrees of a given (Major) key the formulas are:
Minor Pentatonic: 1, b3, 4, 5, b7
Major Pentatonic: 1, 2, 3, 5, 6
This will get you the pentatonics in any key. The minor pentatonic is related to the major pentatonic the same way that a relative minor key (or scale) is related to a major key. Just start of the 6th degree. So, you create the first formula from the second as follows:
Relative Minor Pentatonic: 6, 1, 2, 3, 5
It is easy to check that this is the same result treating the 6 as 1. Think of C maj Pent and its relative minor A min Pent. An interesting note: All the major modes have the same major pentatonic, Ionian, Lydian, Mixolydian. Since we are removing the 4th and the 7th from the list of notes. The minor pentatonic fits over Aeolian, Dorian, and Phrygian.
As for blues, the traditional "blues" scale is the minor pentatonic with a flat 5 added,
Blues: 1, b3, 4, b5, 5, b7
Other answers have provided results in C or another key. I hope this formula in degrees is more general and helps.
There are two standard blues scales, major and minor.
Taking each, add one note to the pentatonics to produce the hexatonics.
C minor pent. is C E♭. F G B♭. Add G♭/F♯ and it's C min. blues.
C major pent. is C D E G A. Add D♯/E♭ and it's C maj. blues.
Which blues scale? I am assuming you mean the hexatonic blues minor scale. There are a number of ways.
1) Take the pentatonic minor scale:
C - E♭ - F - G - B♭
and add a sharpened fourth:
C - E♭ - F - F# - G - B♭
2) Take natural minor:
C - D - E♭ - F - G - A♭ - B♭
and remove the second and sixth degrees, and then add a sharpened fourth:
C - E♭ - F - F# - G - B♭
You may know the blues line for the bass: do mi so la ta la so mi (ta=b7) for the I7.
Mind that the blue notes are b3 b5 b7 (the major 7 is replaced by the b7, the minor 3 and dim. 5th can be added to the 3 and 5 of the ionic scale)
advice: remind some "blues" titles from which you will always be able to develop the blues scale.