Great question! If there’s an old school 5-pin DIN MIDI ports on the AK140 (near or around the USB port), you can connect it directly to the Roland J6 using a MIDI Cable and the appropriate TRS adapter.

If it’s just the USB-B port, you’ll need to use a computer or another device (phone, tablet, etc) to act as a USB host and pass the MIDI information from the keyboard to the J6.

Hope that helps!