A perfect memory could be tested. I read a list of twenty terms to you, and you repeat them back to me from memory. I can compare what you remember to my list, and score the accuracy.
But a perfect auditory memory? It's untestable. How could anyone else know whether you remember what a performance sounded like? How can you yourself know if you remember it correctly, or if you just think you do? You're asking us to believe you, based on faith.