Supposedly, octopuses can't hear or at least there is no identified physical aspect of hearing. However, you are not the only person to report reaction to "sound". Octane's tank was on a shelf that was attached to the laundryroom wall. When the washer went into spin cycle he would react and I had to stop washing clothes after lights out. It may be that the base in the music makes a similar vibration on the tank. It might be an interesting experiment to find something with a lot of base and then try turning the base off and using music with very little to see if there is a difference in reaction.