Actually, its entire tune is the note B-flat, but 57 octaves lower than middle-C, or one million billion lower than what the human ear can hear. It is “the deepest note ever detected from an object in the Universe.”
There’s a black hole in the Perseus galaxy cluster and it’s singing a sad tune in the key of B flat
Joshuah Bearman
Joshuah Bearman has written about CIA missions, jewel thieves, deranged private investigators, aspiring Fabios, bitter rivalry among dueling Santa Clauses, and the metaphysical implications of being the world's greatest Pac Man player. His article for Wired became the movie Argo.