BY FRED KIRSHNIT [NY Sun, 12 December 2005]

Imagine how difficult it must be to hold a position as an official church composer when your country changes religions. Now imagine that there were three such changes in your lifetime, and you will have some idea of the trials and tribulations of Thomas Tallis, whose 500th birthday was celebrated Saturday evening at the Church of St. Paul the Apostle. For Tallis to have kept his head - both literally and figuratively - is a testimony to his subtle compositional skills and his natural penchant for humble quietude.