Check out Zone Music Player for iPhone! With this app you can play songs from your music library and view effects that will speed up or slow down based on average sound power in decibels.

Zone Music Player will display your music files in order by song names, grouped by artist name or grouped by album names. Tapping on song will start the music player which you can open from the navigation bar where the play icon will be displayed if music is playing. Also, when the app starts, all music from your library will be displayed in the "Songs" tab.

Zone Music Player has standard features: previous and next song, play or pause, repeat and shuffle. In settings you can share app info on Facebook and Twitter or this info can be shared via mail.