MIDI is a communications standard, which allows electronic musical instruments to communicate with computers and vice versa. The musical instrument e.g. an electronic keyboard must be attached to the computer through a MIDI interface board. Sometimes this interface is a separate box, more often it is built into the computer sound card.
The purpose of the MIDI interface is to take the MIDI signal and synthesise a soundwave capable of being played by the sound card. This synthesis can be carried out by either Frequency Modulation or Wavetable Synthesis. Frequency Modulation (FM) Frequency modulation combines several simple waveforms to produce a complex waveform. The wider the range of waveforms, the more realistic the sound will appear to the ear. Because of the complexity of an instrument sound, for example a piano, sounds created by frequency modulation don’t sound very realistic. Wavetable Synthesis Wavetable boards synthesise the sound by playing back pre-recorded samples of real instruments. These pre-recorded samples are stored in a ROM on the sound board. The quality of the synthesised sound will depend upon several factors:
Because the board is playing back a prerecorded sample of the instrument, wavetable boards sound more realistic than frequency modulation boards. Most MIDI synthesisers have at least 127 different instruments which you can use. These include orchestral sounds, synthesiser sounds and special effects. For example:
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