Compound there are two sentences connected by a semicolon, you can tell because they each have their own subject (the musician, she) and their own verb (preform, had).
The Mayas and the Roman Empire invented a calendar, they were so advanced in astronomy. On the other hand, both had their own systems to write: Mayas had hieroglyphs and the Roman Empire Latin. Finally, both cultures were polytheistic, which means that believed in many Gods.
<u><em>-SiennaZoeMutty</em></u>