Just my thoughts
when you said "I plug MIDI IN of the interface cable into MIDI OUT of my Yamaha PSR 270 MIDI keyboard. I plug MIDI OUT of the interface cable
into MIDI IN of the keyboard. (Keyboard's MIDI OUT port works fine- I tested it with a Roland Sound Canvas)" .. you *may disabling the USB out when you connect the 5 pin MIDI Out to anything.
Some devices might detect that.


I do not work here, but the benefits are still awesome
Make your sound your own!