Doing this right now, actually got a really cheap usb to midi cable off amazon just so I could use some midi gear into my desktop at the studio (have an apogee duet…no midi) and it works great plugging it directly into ipad via the camera connection kit. No external power source or hub required, sequencing Waldorf Nave and resampling it into OT, sounds awesome. YMMV with the cheap usb to midi cables though, mine is just some no-name brand. I also have the griffin studio dock which is great for sampling the OT back into the iPad.