Photo: Peter Luehr If album sales, longevity of career, position on the leading edge of audio technology, reputation in the music business, and involvement in many of the most important albums in history are the measurements, Bob Ludwig is the GOAT (footnote 1) of music mastering. "I'm an old goat, anyway," he joked during our multiday, many-hours conversation, centered around his recent retirement announcement and his five-plus decades as a mastering engineer.