Ben...
I purchased a Macbook Pro and Logic Pro software about a year ago (Logic Pro version 8 was the latest at the time) in order to record some original ballads that I had arranged and composed using a Yamaha Clavinova CVP-307M. There are two different elements to recording when starting from a piano / keyboard / synthesizer.
One element is the actual musical note information, the specific notes that you are playing with your hands on the piano / keyboard. This musical note information is able to be captured by the computer in real-time while you are playing the piano for purposes of having the computer use your Korg X50 to playback the song at a later time. This scenario of playing back musical note information uses the MIDI standards that date back to the early 1980's.
Another element is the actual sound that the Korg X50 can generate using the sounds that are built into the Korg X50. You can get a computer to record the actual sound being generated by the Korg X50 as well.
I will explain the physical connections for both scenarios:
For starters, you will need to purchase an external audio device that will add some additional connections to your Macbook Pro. This device will create the MIDI connections to and from your Korg X50, and the same device will also have audio input jacks in order to capture the sound being generated by the Korg X50. This device will connect to your Macbook Pro using either a Firewire or a USB connection. The Macbook Pro comes with a Firewire 800 port which is different from the older Firewire 400 port. The audio device you purchase may require Firewire 400 and not 800, so you will have to purchase an Express Card in order for your Macbook to have a Firewire 400 port to connect to the audio device you'd be getting. ( I had to get an express card for firewire 400 in order to connect my audio device I purchased from M-Audio, model Firewire 410). The Firewire 400 express card would slide into the small, rectangular slot located on the left side of the Macbook.
Once you have purchased and connected the audio device to your Macbook, you will have two, round 5-pin DIN connectors on the audio device and the back of your Korg. These 5-pin, round connectors are the MIDI in and out connections, and these will be used to send and receive musical note information between the Korg and the Macbook. You would purchase two 5-pin MIDI cables at your desired cable length; typically a MIDI cable is available up to 15 feet in length.
To have the computer record the actual sound coming from the Korg, you would simply connect a quarter-inch audio cable from the Korg output(s) to the quarter-inch audio input jack on the audio device connected via USB or Firewire on the Macbook. If you only connect the Left audio out to the computer, you can use the Logic software to capture the sound in stereo in order for the finished recording to have the sound on both the left and right speakers.
