Using iPad or iPhone as an AU host for my KEY 37?

Hi. The 37 has a MIDI via USB input and output ports. Can I plug in my iOS device via USB, control it via MIDI track (for example some synth like OB-Xd or ODESSEi) and record the digital signal back into an audio track on the 37 via USB or Bluetooth audio? Or do I need to use an external AD/DA converter? Would my iConnectMIDI be compatible with an MPC? That way I could use outboard processing power to my iPad instead of buying tons of plugins for the MPC that it can't handle anyway.