Wayne Parham Messages: 18789 Registered: January 2001
Illuminati (33rd Degree)
A duct will modify the cavity resonance of a drum, so that may be why he's using it. Even if it's not attached to the drum, the duct by itself will create a standing wave resonator. Both or either kinds of resonances can be used, and he may like the interesting sound it creates. Or he could be doin' it just to make us wonder about it.