If you've got a keyboard, check if it has USB or MIDI ports. If it does, you're in luck.

If you've got both, USB is simpler. Get a driver from the keyboard company's site and connect it with a USB cable. (Check if the driver is compatible! For example, Casio USB doesn't work on Macs.)

If you're stuck with just a MIDI port, you can find a good MIDI-to-USB adapter for around $30. Price and brand don't make a difference. If it's going to work, it'll work 100%.

I've tried this adapter on lots of computer and keyboard combinations. It worked every time and I didn't even need the driver. It's got nice long cables, too.

	Nearly the most affordable way to start playing the game. 61-keys, no built-in speakers, but only $130.
	61-key Yamaha with lots of features and built-in speakers. You can find it for about $200.
	Full 88 key Casio for about $400. (Requires that adapter.)