Connect a 1/4-inch TRS cable (a standard instrument cable) to the left output jack on the back of your Yamaha keyboard or synthesizer. You should see the word "Left," "L" or "L/Mono" written directly above the jack. For stereo sound, you can connect TRS cables to both the "R" and "L" jacks, but you will need an audio interface to connect both cables to your laptop. An audio interface works as an external sound card, and resembles a small module with multiple instrument ports, that you can connect to your computer's USB or FireWire port.
Connect a 1/4-inch to 1/8-inch cable adapter to the opposite end of your TRS cable. This will enable you to connect the cable directly to your laptop. If using an audio interface for stereo sound, you will not need this adapter. Rather, plug both of your TRS cables into two quarter-inch "Line-In" or "Input" jacks on your interface. Then plug the connected USB or FireWire connector into a corresponding port on your laptop.
Open a digital audio program. In order to play a Yamaha through your laptop, you must run a digital music program that supports audio playback. You can use any popular recording program, like GarageBand, Mixcraft or FL Studio, or download a free digital audio program from the Internet (see Resources).
Open the "Settings," "Preferences" or "Options" window in your selected program. You will almost always find this option under your menu bar at the top of your screen, usually beneath the "Tools," "Edit" or "Settings" menu. If you use a Mac, the option will most often read "Preferences," and appear beneath the name of the software in your menu bar. For example, if you use GarageBand, you would click the word "GarageBand" on the left side of the menu bar, and select "Preferences" from the drop down menu that appears.
Click your "Audio" options tab in the "Options" window, if your program separates your options into different sections or categories. Locate the "Input" or "Audio Input" heading on the page and select your input source from the options that appear. If connecting your Yamaha directly to your laptop, choose "Line-In" as your input source. If using an audio interface, choose the name of your interface from the list. Click "OK" or "Apply" when you finish.
Turn on your Yamaha instrument and your audio interface (if applicable) and begin playing the instrument. If your audio program uses a multi-tracking environment, which means that different recording spaces appear in a list for layering parts of a song, you must select a blank track before you can begin playing. Your tracks appear as horizontal spaces stacked from the top to the bottom of the window, like lines of a sheet of writing paper. To select a blank track, just click the title, which usually appears in the left column, and reads "Audio Track 1," "Audio 1" or "Track 1."