Synthesia, Piano for Everyone

Already have a keyboard? Need to connect it to your computer?
USB and MIDI ports

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%.

(One caveat: DO NOT BUY the M-Audio MidiSport Uno adapter. I've heard from more people having trouble with that adapter than all the other problem reports combined! Save yourself some trouble.)

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

Don't have a musical keyboard?
Yamaha YPT-310 An entry-level 61-key Yamaha with MIDI ports (so an adapter is required). $150
Yamaha EZ-200 Bundle A great lighted 61-key Yamaha bundle with stand. You will need the adapter like the one above. $170
Yamaha DGX-230 Bundle A mid-range 76-key Yamaha bundle. It has a USB port, so you don't need an adapter. $390