[update] OK, so the problem is the clacky sound that new dundun skins have on stick impact.
Over these months I've done some experimentation, but still haven't found a magic solution.
- tried to tan the hide with oak bark. overnight did not work, two days did not work, either. maybe the solution wasn't strong enough (but I did not have more bark). the brown color of the skin looks nice, though
- tried the battery acid method (google it). overnight soak did not change the sound appreciably, and I did not want to leave it longer in the sulphuric acid solution
- tried several coats of neatsfoot oil. did not do a damn thing
Now recently one experienced drummer told me that in Guinea they sometimes apply karite butter to the skin and wring it with hands many times to soften the skin. His dunun prepared with this method sound wonderful. Gotta try this. [/end update]