First of all, thanks Winslow for the great discussion. The song is in D that's why I was using a G harp (2nd position), but all of your comments still apply. I got the scale from David Harp's book on basic music theory and he said it was a good way to start C&W, that is, start with the two notes before the root and then progress up a "C&W" scale. The book includes sections on pentatonic scales but I have to check what the differences were between the pentatonic and C&W scales.
Now about bending notes. The best and easiest to understand description on the physics of bending/overblowing notes is in Steve Baker's Harp Handbook. The way it works is this. The lower 6 blow notes are lower in tone than the lower 6 draw notes. You can bend the draw notes down to within a semitone of the blow note. This is why the 5 draw bend is flipping everyone out because there is no discreet semitone between the two notes. You do however, in my opinion, get a bluesy distortion of the 5 draw note that sounds good.
Anyway, that's what you are hearing. Now to make the sound is a little tricky. Drawing of course activates the draw reed, blowing vibrates the blow reed. When you draw bend however, you are directing airflow up to the blow reed and activating it. This activation is different than when you are just blowing on it though and thus, you get a different note. So when you draw bend, you are really raising the pitch on the blow note.
That last paragraph must sound like voodoo, but it's the truth. The reason different airflows affect the reed differently is due to the offset of the reed. The reed is usually set up slightly higher than level in the reedplate. When you blow you push the reed down, past level, until it hits the right tension and snaps back. This is the vibration that sounds a note. When you draw bend, your airflow is actually pushing the reed UP farther than even its offset until it hits the right tension and snaps backs. This vibrational frequency is different and so the note sounded is different.
If you still don't believe me, take the covers off of your harp. Go to a mirror and draw bend a note. You will see the blow reed vibrating. Put your finger on the draw reed and it will still sound the note.
By the way, overblowing is the same phenomenon, but this time you are pushing the draw note in a different manner than when you simply suck on it.
