To do so, select a song and press Command-I to open the Get Info window. Click the Options tab, and you'll see several settings that you can adjust for the song. In the Equalizer Preset pop-up menu, pick the setting you'd like for that song and click OK. Not only will the song always play with that EQ preset on your Mac, but the preset will carry over when you sync that song to an iOS device. If you create a custom preset in iTunes through the Equalizer window, however, those changes won't carry over to your iOS device. Also, if the EQ on your iOS device is set to Off, the device will not play the preset you've selected for any song. And keep in mind that using EQ can have a negave impact on your battery life.
Other EQ apps
If you want more control over EQ in iOS 7 — and you're willing to forgo using the built-in Music app for playback — you can choose one of several apps that offer lots of additional flexibility and functionality. For example, Onkyo's free HF Player brings touch control to custom EQ settings.
In the app, you select the song from your Music library, and then tap the Equalizer button. Push up on the frequencies you want to boost or drag down on the ones you want to lower. You can create detailed custom settings and save them for later use. Like the built-in iOS EQ, the app applies that preset to all songs, but switching within the app among your choices while you're playing a song is a lot easier.
Aphex's Audio Exciter takes a different approach to EQ. Instead of having access to specific frequencies, you control Tune, Harmonics, and Mix settings, which the app uses to tweak the sound output. The advantage of this method over a standard EQ is that the app keeps all the levels in the song balanced, resulting in a mix that hopefully is more similar to the original. The app requires a $1 in-app purchase to unlock this functionality, but you can try it for 5 minutes a day before you buy to see if it's worth it.
The biggest drawback of most EQ apps is that they work only on DRM-free files hosted on your device; if you've joined the streaming music revolution from Beats, Spotify, Rdio, and others, you're out of luck. If, on the other hand, you're a fan of TuneIn's streaming radio options, check out Elephantcandy's $5 Radio EQu. It applies preset or custom EQ to any station available through TuneIn. (The developer says that the current version of the app has issues with the 64-bit architecture of the iPhone 5s and the iPad Air, but promises that a fix is in the works.)
Whichever option you try, you owe it to your ears to give an EQ app a try. You may find a whole new world of listening — no new headphones required.
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