MIDI stand for Musical Instrument Digital Interface. It’s a communications standard agreed upon by musical instrument manufacturers in 1982 to allow different brands of electronic instruments such as keyboards to interconnect with each other. This connection capability also includes personal computers.
The most exciting aspect of connecting a MIDI keyboard to a computer is the capability of recording and editing music played on the keyboard with computer software. The music can then be played back from the computer’s speakers or played remotely through the keyboard. In addition, a musician using MIDI can control numerous keyboards from just one, playing them by "remote control" for a bigger sound or for different sounds, either for recording or in live concerts. Many of today’s keyboard-based artists, such as Yanni, produce their albums this way, and in fact many of the live performances you hear in concerts are reinforced with MIDI-produced music. There are even MIDI devices to control concert lights and to adjust sound levels.
MIDI can be thought of as being similar to the old piano rolls — rolls of paper with holes in them that could mechanically trigger the keys in specially-made pianos, player pianos, to play by themselves. Instead of holes in rolls of paper, MIDI-compatible instruments respond to electronic signals sent by another instrument or by a computer. These signals consist of commands and codes which tell the instrument what note to play and for how long, as well as how loud to play and sometimes what special effects to use. Keyboards are not the only kinds of MIDI instruments, however. There are MIDI adapters for guitars and various drum and percussion devices, as well as wind controllers for such instruments as saxophones and clarinets.
In order to connect a keyboard to your computer, the keyboard must have the proper sockets on the back, and the computer, whether PC or Mac, must have the proper connector, called a “MIDI interface.” Virtually all PC sound cards used today have built-in MIDI capabilities. The problem is, though, that to save space, the MIDI input path is through the joystick socket, which requires you to buy a MIDI adapter with "MIDI in" connections on one end and a joystick plug on the other end. Fortunately, they aren't very expensive. A computer equipped with a MIDI-capable sound card thus becomes somewhat like a computer-controllable synthesizer. You can create musical notes on your computer without a real music keyboard, but you must either place them on the screen with a mouse or generate them from your computer keyboard, neither of which is as convenient as using a real music keyboard.
A computer sound card generates the sounds of many standard instruments as well as some electronic sounds. Most sound cards these days employ wavetable synthesis, meaning they contain digital recordings of actual instruments. Older sound cards tried to approximate instrument sounds synthetically from electronic signals which didn't sound very realistic. You can play a musical part on a keyboard — say, a flute melody — which then appears on your monitor either as standard music notes or as colored bars. You can then edit any mistakes or duplicate repetitive parts. Then you can play another part — say, a drum beat — while hearing the music you already recorded. Layer by layer you can add each part until you have what sounds like a full band! But instead of actually recording the sound, only the musical commands needed to trigger the notes are being recorded, just like punching the holes in a piano roll. I used these MIDI techniques to create my music album, Black Hills Gold.
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