This is found on the way to the training area on the ground floor of the safehouse, where you’ll have to find a hidden code to play the piano, which, in turn, will lead to more safehouse puzzles ...

To solve the piano puzzle in Black Ops 6, you need to play the Mn, Pe, CN, Ao, Pe keys, in that exact order. The door to the right of the piano will open when you do this, leading the way to the ...