Your MIDI keyboard should now be successfully interfaced with your computer, potentially via your audio interface. This ...

That’s it on the left, next to a standard MIDI cable plug. The whole thing is so small it fits inside a MIDI plug and can run off the power supplied by the MIDI output, driving a small pizeo buzzer.

It can connect via a standard MIDI cable and then be used to control anything you want. The only thing missing is the ability to transmit velocity data, but that’s certainly not a deal breaker.