[JLMounce]

Depends on the construction. If it's an absorption style muffler, the longer case will make the car quieter. Typically this does reduce drone as well, but not always. Drone is a resonant frequency and when it occurs it's because the exhaust pulses traveling through the pipes and into the muffler are bouncing around in a chaotic way that cancels some frequencies and amplifies others. Because of this, going to a longer muffler may not always eliminate drone, though you can almost be assured that it will at least lesson it. Of course the trade-off is that the car will be quieter everywhere.

This is why an X pipe works so well to calm down drone, it focuses the exhaust pulses and smooths them out. The trade-off of course being that you typically lose some of the lope from your cam and it has a tendency to create a higher pitched note than some people prefer on their classic muscle cars.

A chambered muffler is a whole different animal. It has tuned length runs that force the exhaust pulses to bounce in a specific way to attenuate frequencies and cancel others through an audio process known as phasing. It's what gives chambered mufflers their characteristic sound. Because there's no actual absorption of sound, going to a different sized case doesn't always mean a reduction in sound level or drone.