The default iPhone music player lets you adjust equalizer to enjoy playing songs more. To set and change equalizer on iPhone 5, iPod touch and other iDevices, do as follows:
1. Tap to open the Settings app on your iPhone
2. Scroll down to Music and open it.
3. Scroll down to Playback settings and tap the EQ option
4. As you see, there are lots of pre-set equalizers you can choose from. Some of the available equalizers in the Music app on iPhone are: Acoustic, Bass Booster, Deep, Lounge, and Small Speakers.