For a quick summary of this topic, have a look at Blues scale.
The G-sharp blues scale has 4 sharps.
|Note no.||Note name|
|1||The 1st note of the G-sharp blues scale is G#|
|2||The 2nd note of the G-sharp blues scale is B|
|3||The 3rd note of the G-sharp blues scale is C#|
|4||The 4th note of the G-sharp blues scale is D|
|5||The 5th note of the G-sharp blues scale is D#|
|6||The 6th note of the G-sharp blues scale is F#|
|7||The 7th note of the G-sharp blues scale is G#|
Middle C (midi note 60) is shown with an orange line under the 2nd note on the piano diagram.
These note names are shown below on the treble clef followed by the bass clef.
The white keys are named using the alphabetic letters A, B, C, D, E, F, and G, which is a pattern that repeats up the piano keyboard.
Every white or black key could have a flat(b) or sharp(#) accidental name, depending on how that note is used. In a later step, if sharp or flat notes are used, the exact accidental names will be chosen.
The audio files below play every note shown on the piano above, so middle C (marked with an orange line at the bottom) is the 2nd note heard.
The numbered notes are those that might be used when building this note scale.
Note 1 is the tonic note - the starting note - G#, and note 13 is the same note name but one octave higher.
|Note||G#||A||A# / Bb||B||C||C# / Db||D||D# / Eb||E||F||F# / Gb||G||G#|
The next 3 steps (including this one), show how the natural minor scale is used as a basis for the minor pentatonic scale, which in turn is used to construct the blues scale in this key.
To understand why this scale has these sharp and flat note names, have a look at the G# natural minor scale.
The minor pentatonic scale is made from the 1st, 3rd, 4th, 5th and 7th notes from the natural minor scale above.
To understand why this scale has these sharp and flat note names, have a look at the G# minor pentatonic scale.
To construct the blues scale from the minor pentatonic scale in the previous step, take the 4th note of that scale(note D#), flatten it, and insert it before the 4th note position of the same scale. This note D is the blue note that gives the blues scale its distinctive sound in this key.
Another way to identify the blue note is to take the 5th note of the natural minor scale from 2 steps above, (which is the same as note 4 as the minor pentatonic scale), and flatten it.
Yet another (more complex) way to identify the blue note is to take the Diminished 5th note interval based the tonic note - G#-dim-5th.