Suggestions for muscle car sound muffler without drone

This guy installed resonator tubes on his Shelby Mustang with electric cutouts on the resonator tubes. You can hear the difference with and without them. He also says with them he can hear the stereo and talk in a normal tone of voice in the car.

[ame="http://www.youtube.com/watch?v=ijwxKDVnAec"]Cruise Loud or Quiet - Exhaust Cutouts Installed on Resonator Tubes - YouTube[/ame]