SP Studio Systems SP-12 - Manual (Page 90)

APPENDIX
© E-mu Systems, Inc. 1985 Page 90
Enhanced by The Emulator Archive 2002 www.emulatorarchive.com
APPENDIX D: UNDERSTANDING MIDI/SMPTE
MIDI is causing a certain amount of confusion among musicians. Fear not -- it’s not
all that difficult to understand, and the SP-12 makes it particularly easy to deal with
MIDI.
For those of you who aren’t that familiar with MIDI, we’ll first answer some common
questions. -
What does the MIDI cable do?
An instrument already has an AC cord that carries electrical current, and an audio
cord that carries audio signals to an amplifier. Now you have a third connection: the
MIDI cable. This carries neither audio nor power, but transmits information about the
status of the instrument to, and receives “status reports” from, other MIDI
instruments. This information is coded in a computer language. . a somewhat
primitive language with few words and several dialects, but a language nonetheless.
What does MIDI stand for?
MIDI stands for Musical Instrument Digital Interface. You already know what “musical
instrument” means, so that takes care of the first half of this phrase. Digital means
that the instrument’s information is conveyed in digital, or computer, language.
Interface is the term for the actual link between instruments, where data passes from
one instrument to another. So MIDI is a link between musical instruments that speaks
data in computer language.
How can information control a synthesizer or drum machine?
First we need to know a bit about computers, since MIDI instruments have
microcomputer souls...in fact, MIDI could not exist without microcomputers.
Computers are decision makers, and they base those decisions on the data they
receive. However, to be useable by a computer any data has to first be translated
into a number-based language that the computer can understand. Actually, when you
press a keyboard key with a computer-based instrument, you are not directly
[[controlling the sound source. Instead, each time you close a keyboard switch you’re
sending a number to the computer, and this number tells the computer what note you
want it to play for you.
The computer’s “window on the world,” where it receives and transmits
numerical data, is called its data - The computer looks to see whether any
information is on the data bus, and if so, acts on this data. For example, if it
sees a digital “word” that says “play F#” on the data bus, it will do as the data
commands and control a sound source so that it plays an F#. However, note
that the computer doesn’t care whether this word is placed on the data bus
due to closing a keyboard switch or striking a drum head -- once MIDI
translates a note into computer language, the note becomes compatible with
any device that speaks the same language. MIDI provides access to the
computer’s data bus and selects which device will be “on the bus” at any