Watch the D min 7 Tuning online guitar lesson by Vicki Genfan from Essentials: Open Tunings

If you play only the 4 highest strings on the very first chord (D7) you'll have a moveable chord which means you can move this around anywhere on the neck! How is the ringing on your harmonic brush on the Am7 chord? Make sure you're holding your left hand finger right on the fret, and that you're releasing very quickly to get the loud ringing harmonics. If you're new to this, please take the time to slow it down and get the right touch. You'll know it's right when you hear the ring.