The GB2i is the perfect interface between your Guitar or Bass and Strumtune or the other Effects pedal APP. Simply plug your instrument into the GB2i, and the mini lead from the GB2i into the iPhone headphone jack and start tuning. Its too loud to use the iPhone's mic? No Problem. Simply plug your instrument directly into the iPhone using the Cherub GB2i Guitar/Bass/ iPhone converter. Keep it inline with the THRU jack. You need a little personal time with your instrument? Plug your earphones into the mini earphone jack and start creating. You can use AmpliTube,DigiTech Stomp Shop,GuitarToolkit,TabToolKit,Audiobus,AmpKit+,Reverb.com,MoovFX Echo (Lite),JamUp Pro,iPB,iShred LIVE (The copyright is not owned by us,any related charges is paid by users .) and some other Guitar APP with Cherub GB2i.