Don't know who told you that it confuses enemy boats. Its meant solely for you, the player, to be able to listen to music while you play. It has no bearing on the game world at all. You could have your gramophone blast "You Shook Me All Night Long" while under depth charge attack, and aside from getting a little chuckle from the irony of it, it doesn't affect the gameplay at all.
And if you want to unlock the extra secret bonus gramophone tracks, you have to make a run through the English Channel at flank speed. Really!

:rotfl: