There are many MIDI keyboards are, like the companies that manufacture - Yamaha, Roland, Korg and Casio, among others. After his own big is a must if you are a musician - amateur or professional. It does not take a genius to buy one, but it requires some mental considerations before you want to use to get.
There are many different types of units there - the great piano-types, controllers of small children. Today, most electronic keyboards have MIDI capability then buy your decisions is even greater. If you are looking for a portable keyboard focus on what you want to be transported. Just because it does not necessarily called portable keyboard, they are all easy to carry. That is their strength comes in. by size is generally the number of keys that it is intended.
88 key piano keyboard means. This MIDI keyboards are generally larger and heavier. They are still mobile but can be tedious, especially if you are still on the road. Set up can be a problem depending on where you will use. When on stage then you can have no problem with the room, but if it is at home, then it would be extremely difficult to push something to a few meters in front of the computer next to the keyboard. The same applies to small 76.
Then there are smaller - and from 37 to 25. They are small and lightweight which makes it very portable. For most people are satisfied with smaller units, because you can always do what you can do anything with their larger siblings, but in a smaller package.
That said, the smallest (37 and 25) tend to MIDI controller keyboard, rather than actual piano keyboard. This means that they are used to create other MIDI-compatible instruments and control the music out of them. These machines have a sound system of their own importance, you do not want to hear when you press the buttons integrated. You need a sound card and audio editing system to hear something - your computer will.
Then there are the buttons and knobs to think. Most units have a set of keys, buttons, buttons, sliders, and an LCD screen on startup. The largest unit for other widgets you can. Mesh that with a good software digital audio workstation, and you can almost every instrument sound you want to happen. Of course, most MIDI keyboard and the possibilities it has more the higher the price. Many recommend a simple small keyboard, as it can handle pretty much what most musicians want. This means that it does not matter if you only have a 25-key device, as long as you able to maximize their use, then it is the ideal device for you.