That connector on your sound card, that port that was originally for a joystick, is it not an in AND out cable? If so, you are wired wrong. If not, check with Soundblaster and see what they have for you. I seem to remember WAY back I was using that 15 pin port for MIDI but I had a Y cable that had in and out.

I still can't figure out what you are trying to accomplish. You want to play parts INTO your software or play existing part back on a different sound source (your synth)?

Best case hardware scenario is a USB MIDI interface and a MIDI thru box. Plug in one keyboard as the controller to the MIDI IN, and then plug the MIDI OUT to the input of the thru box. You can find a 1 in 8 out thru box almost anywhere. Like $10-20 bucks used.

I am using the new 1040XTRAEZ form this year. It has just 2 lines.

1. How much did you make in 2023?
2. Send it to us.