Here's a technique for recording keyboards and other sample-based instruments to create a more realistic, or "live" sound. This technique is especially useful if you are trying to emulate acoustic instruments.

Start by splitting the outputs of the keyboard; send one channel to your multitrack recorder (via your mixer, or direct), and the other channel to a keyboard amp (almost all keyboards have stereo outputs so this shouldn't pose a problem). So, what is the effect? The sound moving through air and room characteristics that you get from miking the keyboard amp will create the illusion that the instrument is being played live while the direct recording of the first channel will add clarity. When it comes to mixing, blend the two sounds together to taste. However, I have found that the miked channel should be lower in volume. Bring it up just enough to add the "live" effect to the line-in channel. Mics, amps and rooms add noise and adding in this noise to an otherwise sterile sound will add spice and character. Naturally, the end result of levels and which channel to feature is left up to your personal taste.