According to the folks at Harbinger, I should plug my 1/4" Stereo out from the Casio Keyboard, into Input #3 \ Left (MONO) and all should play well.
Perhaps because the WK-3200 is at least 15 years old, the Harbinger configuration did not work. So, I used a cable with 1/8" stereo cable, with the White/Red RCA Jacks on the other end. I adapted to a 1/4" x 1/8" stereo jack into the keyboard. On the RCA jacks I adapted Mono 1/4" x RCA mono Jacks and plugged those into the Left and Right of the Harbinger Input#3. Now all keyboard play and recorded tracks play with the appropriate volume.
