Shake the flower, root out song in your house, Ipalnemoani, Master of Herons. -- Rejoice!   Perhaps with words you will be pierced, broken to understand, Prince Warriors: earth is all over with. -- Rejoice!   The brilliant Aztec poetic tradition would have all but vanished after the Spanish Conquest in 1521 without the friars who painstakingly transcribed and preserved the poems in the years that followed.   In this new edition of their translations, Edward Kissam and Michael Schmidt--two poets who spent formative years in Mexico--give us powerful echoes of the lyrical and philosophical songs; the songs of rejoicing, sorrow, ritual, and war; the laments made by Nezahualpilli and others as the end of their empire approached; and the epics of myth and legend.   Their introduction is a distilled account of the background to the Aztec empire, its way of life, and its fall, including the role of poetry in Aztec life and how the poems were preserved.   Michael Schmidt, poet, scholar, critic, and translator, is the founder-director of Carcanet Press and PN Review. He studied at Harvard University and Wadham College, Oxford, before settling in England. He lives in Manchester.   Edward Kissam studied at Princeton University and Magdalen College, Oxford. He works at JBS International on a variety of applied research issues related to education in developing countries. He is the author (with David Griffith) of Working Poor: Farmworkers in the United States. He lives in Oakland, California.