Root to crown
The seven energy centers
What each center is, where it sits, and what the material holds about it. Two of the seven are bone and have no cavity to answer a tone, and we say so rather than making something up for them.
Where the familiar rainbow comes from. The red-to-violet chart almost everybody has seen is a twentieth-century Western arrangement, not an ancient one. The 1577 Sanskrit text the system is usually traced to describes the heart as red rather than green and the brow as moon-white rather than indigo, and there is no single chakra system to be faithful to — the source texts range from four centers to more than twenty depending on the lineage. We would rather say that than claim an authority the texts do not give.