Foreshortened heavens // Africa is a pegasus but lost a wing.
Mimicry of ancient tyranny // um.idk. did Africa (the continent) have tyrants?
Chastity had no hold on you // Africa was chaste until she slept with Midas and had a baby.
Gleaming trumpets in royal bands, flighty music // Africa was royalty and she slept with a (golden) Midas (royalty), is known for having a flighty personality