I have an interesting idea: Build an Adaptive Amp. That is, an amplifier that takes advantage of the fact that we humans adapt to the environment.
The Adaptive Amp takes advantage of this fact, alongside precise calibration according to the human auditory capacity, to continually reduce the volume it plays at, but at a rate below the just noticeable difference. Auditory adaptation ensures that people will adjust to the new volume level, within a reasonable range, so they will be able to hear the music just as well, but simultaneously a) saving their hearing from permanent damage and b) allowing you to continuously turn up the volume on your favourite songs without the music getting any louder on average!
Thank you for listening.