The Bwiti consider music an integral part of an iboga ceremony, and having listened to many hours of mcongo mouth harp music my first time, I do feel it has a powerful effect on the experience and assists with the brain defrag. I remember when the music stopped, after all those hours, my brain was entrained so that the falling rain outside kept playing the harp music very vividly in my head for hours afterwards!
However some people prefer a silent reflection with the wood, I know some guys who work with iboga and have a fair amount of experience over many years and they employ silence during their ceremonies. So both are valid I feel. I've attached a mcongo clip that can be looped if that is of any interest.