hi janice, i also like to tune my drums so that they create a harmonic 'melody', but i should stress that's your western trained ear causing that cringing
west african sense of aesthetics can be very different from ours (just check out some of the traditional sculpture). to an african djembefola it matters more that you can hear the different drum parts so some tuning may be necessary and certainly some djembefolas do tune them to intervals that are pleasing to western ears. it depends on their exposure to various types of music, which in turn influences one's personal sense of aesthetics.
i personally don't follow any rules when it comes to tuning drums. i found that trying to aim for 4ths didn't necessarily work for all drums or situations. it depends how the drums are sitting with each other (as well as the amount of time i have before the session) as to how i will tune them!
also, if you're hearing a really unpleasant buzz, just remove the remo. sorry, couldn't resist putting that in