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PART VI Digital Audio Microphones Computer Instruments Audio mixer Audio interface with MIDI I/O MIDI controller MIDI module MIDI module MIDI module Powered loudspeakers 458 FIGURE 16.1 Example of a typical MIDI system with the MIDI network connections being shown in solid lines and audio connections shown using dotted lines. pretty much the same with MIDI. A MIDI file or data stream is simply a set of instructions that pass through wires in a serial fashion, but when an electronic instrument interprets the data, we then hear sound. As a performance-based control language, MIDI complements modern music production, by allow- ing a performance track to be edited, layered, altered, spindled, mutilated, and improved with relative ease under completely automated computer control and after the fact, during post-production. If you played a bad note, fix it. If you want to change the key or tempo of a piece, change it. If you want to change the expressive volume of a phrase in a song, just do it! Even its sonic character (timbre) can be changed! These capabilities merely hint at the power of this medium that widely affects the project studio, professional studio, audio or visual and film, live performance, multimedia, and even your cell phone! THE MIDI MESSAGE From its inception in the early 80s, the MIDI 1.0 spec (which is still the adopted version to this day) must be strictly adhered to by those who design and manufacture MIDI-equipped instruments and devices. As such, users needn't worry about whether the MIDI Out of one device will be understood by the MIDI In of a device that's made by another manufacturer (at least the basic performance level). We need only consider the day-to-day dealings that go hand-in-hand with using electronic instruments, without having to be concerned with data compatibility between devices. MIDI messages are communicated through a standard MIDI line in a serial fashion at a speed of 31,250 bits/s. These messages are made up of groups of 8-bit words (known as bytes), which are used to convey instructions to one or all MIDI devices within a system. Only two types of bytes are defined by the MIDI specification: the status byte and the data byte.