Dr. Ralph Stanley has been singing and playing bluegrass music since 1947, and after more than 50 years, his music has changed remarkably little: his voice may be rougher and more fragile than it was in his youth, but he still sings with a fierce and unaffected mountain purity, and he continues to lead a solid acoustic band that performs this music with a balance of virtuoso skill and little need for flash and filigree. 2011′s A Mother’s Prayer is yet another set of Christian bluegrass numbers concerning the challenges of the mortal world and the salvation and solace of faith, sometimes retelling stories from the bible and other times focusing on the trials of everyday life. A Mother’s Prayer doesn’t contribute anything particularly new to Stanley’s catalog, but does anyone want to hear this man try to reinvent the wheel at the age of 84?