How do I connect a bass guitar to my iPad to use with Garage Band Garage Band for iOS has a mode to use real instruments. The documentation is unclear, however, how to connect those instruments to the iOS device. What options exist to connect an electric bass guitar to an iOS device to use with Garage Band?
Hope this will help?
http://www.musicradar.com/news/guitars/6-easy-ways-to-connect-your-guitar-to-your-iphone-ipad-or-ipod-touch-516544
Or even more specific:
https://gigaom.com/2013/02/09/four-ways-to-connect-your-instrument-to-garageband/
Or you meant something different?