The Scales...

 

Pos No.

Harp Key Scales  
    I II III IV V VI VII  

1

C C D E F G A B  
2 F F G A Bb C D E  
3 Bb Bb C D Eb F G A  
4 D#/Eb D#/Eb F G G#/Ab Bb C D  
5 G#/Ab G#/Ab Bb C C#/Db Eb F G  
6 C#/Db C#/Db Eb F F#/Gb G#/Ab Bb C  
7 F#/Gb F#/Gb G#/Ab Bb B C#/Db D#/Eb F  
8 B B C#/Db D#/Eb E F#/Gb G#/Ab Bb/A#  
9 E E F#/Gb G#/Ab A B C#/Db D#/Eb  
10 A A B C#/Db D E F#/Gb G#/Ab  
11 D D E F#/Gb G A B C#/Db  
12 G G A B C D E F#/Gb  
13 C C D E F G A B  
You'll notice that when viewing the Circle of Fifths, you're going counter-clockwise for the Harp Key.

 

The above "Harp Key" column is the next position harp.  For example 1st position harp is a "C" would be used to play a "C" key song.  Take harp key "F" and you'll be using a 2nd position harp to play a "C" key song.  Notice that the "B" note in column 7 (bolded) changes to a "Bb" in column 4 (bolded).  Hence - by going to a 2nd position ("F" harp key) to play a song in the key of "C", you are getting the "C" scale EXCEPT you are now getting a "flatted 7th", ie, the 7th letter of the "C" scale is now flatted to a "B" in the "F" scale.  If you read across on the "F" scale from column 5 to 7 and then start at 1 again you get C-D-E-F-G-A-Bb.

 

You can get 2nd position another way...

Use the same key harp but start on the 2 draw

Pos No.

Harp Key 2Draw 3Draw bb 3Draw 4Blow 4Draw 5Blow 5Draw  
    I II III IV V VI VII  

1

C C D E F G A B  
2 to get G G A B C D E F  
3 to get D D E F# Eb F G A  
4 A D#/Eb F G G#/Ab Bb C D  
5 E G#/Ab Bb C C#/Db Eb F G  
6 B C#/Db Eb F F#/Gb G#/Ab Bb C  
7 F#/Gb F#/Gb G#/Ab Bb B C#/Db D#/Eb F  
8 C#/Db B C#/Db D#/Eb E F#/Gb G#/Ab Bb/A#  
9 G#/Ab E F#/Gb G#/Ab A B C#/Db D#/Eb  
10 D#/Eb A B C#/Db D E F#/Gb G#/Ab  
11 Bb D E F#/Gb G A B C#/Db  
12 F G A B C D E F#/Gb  
13 C C D E F G A B  
                   
  By playing the "G" scale, for example, on a "C" harp, you get a "flatted" 4th note (F instead of F#)