"In the olden days, the cable from my keyboard went to a soundcard. There was a peculiar arrangement which accepted the MIDI cable and also had a connector for a joystick."

The soundcards of the day had a MIDI interface (connected thru the 'joystick game' connector) which converted the GM commands into 'wave' output music sound, using a table of sampled data for each sound style, eg piano, sax, etc. You used to be able to acquire a 'convertor cable'.

I'm no expert as to whether modern sound cards have this - but with the proliferation of 'on board sound' that means motherboards no longer need plugin sound cards, and may have no 'game/joystick/ connector, I doubt it.

You would thus need a plug in card. You may need to disable the on board sound, or you may end up with 'device contention' - and get no sound at all.