In this tutorial I'll give you a run down of the techniques I tend to use when recording a variety of keyboards including Piano, Organ, Electric Pianos, and Synthesizers. While these are the way that I like to do things, everyone is different so please only use these as a guideline in developing your own techniques!
First I'll talk a little bit about recording the acoustic grand piano. What I usually do is use anywhere from two to three microphones. If I am using three microphones I will place two small diaphragm condenser microphones like a pair of Neumann KM184s or Shure SM81s at each end of the piano as this will pick up the highs and lows. I then place a large diaphragm condenser like a Neumann U87 (although any large diaphragm will do) in the middle to pick up the mids and the general sound of the piano. If I am only using two microphones I will tend to use the small diaphragm condensers on each side of the piano, but will place each of them closer to the middle. Definitely do some experimenting with how far away from the strings you place the mics as this can make all the difference in the world.
Recording an upright piano can be a bit different from recording a grand or a baby grand piano, but the principals are generally the same. I will usually take that same pair of a small diaphragm condenser microphones and place them downwards into the piano after removing the top and placing them a few inches in. The further that you put them in, the most of the hammer sound you will get - which could be exactly what you are looking for but it all depends on the type of sound that you are going for. I've also found that using some PZMs (pressure zone mics) will work pretty well for both upright pianos and grand ones as well.
Next lets talk a bit about recording the organ. Of course like with all electric instrument it is always an option to go direct, but I'll talk a bit about recording a Hammond organ with a Leslie cabinet. The technique that I usually use for micing up a Leslie cab is to use a pair of Sennheiser MD421s both on the top and the bottom of the cabinet. The top will give you the horn and tweeters sound resulting in a high endy type of sound, while the bottom will give you some more bass. I'll then blend the two of the sounds together to get a sound that I like when it comes to mixing...Of course there are a ton of ways that you can do this but it is always essential to give yourself options to work with during the mix stage.
A type of keyboard that I like to use a lot is an electric piano, whether it be a Fender Rhodes or a Wurlizter Electric Piano. I just can't get enough of these keyboards as I really love the sounds that they produce. I will almost always get a direct input signal from these instruments, but will also try to use an amp when I can as well. When it comes to the built in amps that a lot of the Rhodes pianos have, I will almost always put up a pair of Sennhesier MD421s as these work perfect for picking up this sound. There are endless ways to record electric pianos, but a standard set up of getting a direct signal and an amp and blending the two can almost never go wrong...
Last I'll talk briefly about recording synthesizers and digital keyboard based workspaces like the Yamah Motif or Korg Triton. For these types of instruments I simply just a get a direct stereo pair and this usually does the trick. However, a lot of times it can add a lot to recording both the direct signal and an amped version either through a bass or standard keyboard amp as this can add a lot to a performance. It really depends on what type of sound you are trying to get as I've said before there are really endless ways to record keyboards..
While this is by no means a complete list of types of keyboarded instruments or techniques, please use this as a guideline if you use this at all! All keyboards or different and the only way to get your own techniques down is to experiment and try things out for yourself. Have fun!