Spengler did indeed reject linear history. He saw cultures a finite, with a childhood, adolescence, youth, old age, and, finally, death. Hence, all cultures could contained architypes analogous to other cultures, eg: Napoleon = Alexander. This is an excerpt from Decline of the West (Chp. 14. Problems of the Arabian Culture. Historical Pseudomorphoses.) that helps the designation, Magian.
"In a rock stratum are embedded crystals of a mineral. Clefts and cracks occur, water filters in and the crystals are gradually washed out, so that in due course only their hollow mould remains. Then come volcanic outbursts which explode the mountain; molten masses pour in, stiffen and crystalize out in their turn. But theses are not free to do so in their own special forms. They must fill up the spaces that they find available, Thus there are distorted forms, crystals whose inner structure contradicts their external shape, stones of one kind presenting the appearances of another kind. The mineralogists call this phenomenon, Pseudomorphosis."
(Here, I wish G. Bush and co. would have read Spengler.)
" By the term, Historical Pseudomorphosis, I propose to designate those cases in which an older alien culture lies so massively over the land that a young culture cannot get its breath and fails not only to achieve pure and specific expression forms, but even to develop fully its own self-consciousness. All that wells up from the depths of the young soul is cast in the old moulds, young feelings stiffen in senile practices, and instead of expanding its own creative power, it can only hate the distant power with a hate that grows to be monstrous."
"This is the case of the Arabian culture. Its pre-history lies entirely within the ambit of the ancient Babylonian civilization, which for 2000 years has been the prey of successive conquerors. It's 'Merovingian period' (Spengler's time analogy: youth) is marked by the dictatorship of a small Persian clan, primitive as the Ostrogoths, whose domination of 200 years, scarcely challenged, was founded on the infinte weariness of a fellah-world. But from 300 BC onwards there begins and spreads a great awakening in the young Aramaic speaking peoples between Sinai and the Zagros range. As at the epoch of the Trojan war and at that of the Saxon emperors, a new relation of man to God, a wholly new world feeling, penetrated all the current religions, whether these bore the name of Ahuramazda, Baal or Yaweh, impelling everrywhere to a great effort of creation. But precisely at this juncture there came the Macedonians - so appositely that some inner connection is not altogether impossible, for the Persian power had rested on spiritual postulates, and it was precisely these that had disappeared. "
The mistake modern historians have made, Spengler goes on to say, was/is to assume a border existed where the Classical languages ended in the east. In fact, a younger, culture alien to the aging-dying Apollonian culture, existed independent of philology, and spreading rapidly westward. This is the Magian culture.
More on music, ala Spengler, later.