How to make the music player on my iPhone play music louder?

I did a comparison of how loud the music on google play music is compred to the iPhone music player

The google play music plays louder compared to the original music player (tested it by putting the music files on both services)

Is their a way to increase the volume of the iPhone music player?

You could buy a speaker if you want to play it alone. When with people, it will be loud if you you crank up the volume while wearing headphones and it will be louder that it would be just playing out from the phone