The best way to record keyboard performances, though, is to bite the bullet, break the bank, and buy an actual, external musical instrument. It might take any of these forms:
A MIDI controller. MIDI (pronounced “middy”), you may recall, stands for musical instrument digital interface. It’s an electronic language that lets musical equipment and computers communicate over a cable.
Because your Mac is perfectly capable of playing any of hundreds of musical-instrument sounds (like the ones built into GarageBand), you don’t really need an electronic keyboard that can produce sounds; all you really need is one that can trigger them.
That’s the point of a MIDI controller; it looks and feels like a synthesizer keyboard, but produces no sounds of its own. It makes music only when it’s plugged into, for example, a Mac running GarageBand.
Apple sells (or, rather, resells) a MIDI controller for $100 called the M-Audio Keystation 49e. If you can live with 49 keys, it’s a very nice keyboard. It draws its power directly from your USB jack, so you don’t need a power adapter, and it’s velocity-sensitive, which means that its keys are touch-sensitive. The harder you play, the louder the piano sound, for example.
A MIDI synthesizer. If you already own a MIDI synth—an electronic keyboard that provides an assortment of sounds and has MIDI connectors on the back—there’s no point in buying a MIDI controller. You can connect the keyboard directly to your Mac and use it the same ...