Here are the audio tracks for Third Position Blues Harmonica articles by Tony Eyers in Harmonica World
The first track is a 12 bar blues backing in A. Use a G harmonica to play over this.
The next track is a 3rd position blues scale, on a G harmonica, starting on a 4D.
This track is the 3rd position blues scale played three times, up and down starting on a 4D, with a backing track.
This is the bottom octave blues scale. The notes are 1D 2D" 3B 3D"' 3D" 4B 4D, sounding like this