PocketGK with iRiffPort is the best bass guitar amp system for practicing with your iTunes music, supporting Pitch Shift and Slow Downer for learning and it’s just been updated. Check out the great improvements in What’s New below. This is a free update but if you haven’t already downloaded this app you can do so here. It retails for $4.99/£2.99/download. What’s New?   Now supporting iOS version 4.2 or later. 
Improvements as follows: 
- Playlist support for music player 
- Noise Gate controls adjusted 
- Song Trainer Speed control adjusted 
- GK 2012 Product Catalog 
- bug fixes Demonstration video