Hi SanRavRC,
High Resolution feature that build-in on the phone allows you to enhance the audio quality with the normal MP3 music that we have.
However to fully enjoy the high res audio is still best if you own some high res audio files.
Where to get it? It can be a high res audio CD that you purchase from a retail store and rip it with selected software that supports that.
High res is 24bit and above you can also purchase the digital track example from this webpage :
http://www.hdtracks.com/Further info about this, you may refer to the link below and there is some webstore that allow you to purchase digital copy of high res audio.
http://discover.store.sony.com/High-Resolution-Audio/#whatsHraHope this answer your question.
Regards.