Bernie,
The SD40 has three USB hosts for MIDI as well the USB device port for PC connection. The three USB hosts are indeed class-compliant. If your M-Audio 61 is class-compliant, it should work right out of the box with the SD40. My SD40 recognizes the Korg Microkey Air by name and plays right away. So you don't even need to involve your Kenton USB midi host. Since the Korg Air is also MIDI over Bluetooth, it can even be wireless by using a little Bluetooth MIDI receiver plugged into the SD40.

Chris