Very true. I can remember hearing a Indian tune on the discovery channel one day (hah..yeah i watch the discovery channel.) and it was clearly in Bb, and oriental music is clearly pentatonic. All music will have a tonic relationship, like you could play a melody in G major, and although you may not play the G you can still hear its impression "color" in the tune your playing. Unless your playing Jazz, then you may find that the tonal center is a mode. A cool twist to the tonal or tonic idea.