Garage Band is Apple's proprietary software. I believe that there are some apps that will allow micro-usb to MIDI but the problem is low latency audio. Android has never been fast enough for real time music processing. In the best case, latency is somewhere around 100ms on late model nexus devices running stock android. This is about as integrated as software/hardware get on our OS. Unfortunately, this problem has been around since day one and was number 2 on Google Code's bug report forums for several years until Google locked the topic thread. There are several reports that proper low latency will be implemented on L, but honestly, I have been chasing down that rabbit hole for many years and finally just gave up and got an iPad to complement my S5. Audio in/out is like 5ms on proper iOS apps. This has been Android's Achilles heel from the start for live music processing.
Maybe someone else is more up to speed on the issue and can convince me to sell my stupid iPad for a Nexus 9 with proper low latency real-time audio processing. I have lost all hope at this point.