What is here being attempted is an overall comparison of the various elements of Jewish worship that were forged in the contexts of the two powerful monotheisms of Islam and Christianity in the middle ages. Some preliminary impressions are given of what in Jewish prayer originated where, and when, and some conclusions reached about how the influences may have differed, depending on the religious empires in which they evolved. It becomes clear that in each of the two milieus there were dynamic developments that may partly have been inspired by the general cultural environment. The topics briefly discussed include centralization, literacy, sects, poetry, gender and martyrdom. Special attention is also paid to the Spain where the situation was different in that the Jewish communities there lived for centuries under Islam and then found themselves under Christian rule.