there's an amazing video on youtube about how metal bar/gong instruments (like gamelans) have different overtones, and regular western intervals instead of being consonant (like with vibrating strings) are dissonant - even perfect 5ths - and a totally different set of intervals are consonant (slendro and pelog tunings are a bit different for this reason).
thinking about it, each drum here would have totally different ideal scales to the others.
A friend told me that a Dutch university ordered a custom gamelan tuned chromatically. It was a total failure and sounds terrible. The gamelan are made one by one w the oldest member of the group making his first and everyone tuning theirs from his down in turn, IIRC.
Also you can draw your own drums! What! That's so cool