Insanity #05 28 февраля 2000

Железо

Midi Interface 2 - the continuation of the description of the Midi interface.

      Eeї ° √ ¤ ¤ √ ∙ ° ўeE MIDI Interface. Part 2 eї ° √ ¤ ¤ √ 
∙ ° ўeE 



(C) Dr.Dismal



    Well, Well, I went on a crazy story about MIDI.
Since the complaints are about the materials in In5tY was not, 
we will assume that this is someone so interesting.



                        Minutes of MIDI.


    In computing the protocol to understand the agreement,
concerning the control procedures for information exchange 
between interacting objects. This should include

Control message format, command stream, and
actions in case of mistakes. MIDI protocol is based
on the fact that only one device always sends commands,
another accepts them and performs. Teams mean offensive
Some events, such as a keystroke or her own
release. In the absence of any instructions from the
transmitter, the receiver is waiting. Therefore, in order
to play the note you want to send 2 teams: "insert
note "and after the duration of the note, click off
note.


    Commands are one-, two-, or trehbaytnye. The first byte
command determines the action produced by the team, and is 
called a status for them may be followed by one or two bytes of 
data. The most significant bit status byte unit, a data byte - 
always zero, so you can send 127 commands. Consider 3

byte command to include the note "; trehbaytnuyu, with status
byte # 90. The first byte of data - the number of notes, the 
second - the speed keystroke. The lowest note is the number 
zero, the most Top 127. Before the first note an octave 
corresponds to the number # 3C. 


    Speed ​​keystrokes - this is an optional parameter
designed to accentuate the music. Its numerical value
and from 0 to 127. But we should remember that both the 
receiver and transmitting devices are programmed music system

transposed, and the "velocity sensitive" may be difficult
way depend on the actual speed keystrokes.
Therefore, the absolute scale of the correspondence between the 
transmitted and real parameters of sound does not exist.



    For simplicity, we assume that there is no transposition. 
Then, to include a note before the second octave, you need to 
pass byte # 90, # 48, # 7F. To play

chords polyphonic synthesizer, passed sequentially
Several teams "to include a note" - individually for each note 
in chord. Time delay between the teams is low - for

chord of 3 notes of not more than 1,8 ms. and on hearing it was 
not audible. 


    There is another team for the rapid volume changes
music, but in time - "pressure on the press." Her
transfer of modern keyboards, which measure the effect of 
depression. K Unfortunately, the same commands to change the 
pitch not exists.



    Partly it is replaced with the command "wheel position 
change tone, affect the frequency of all commitments at the 
moment the music. 


    Often, during the game you want to change the timbre
a tool to manipulate the effects. In such cases,
use the modulation wheel, pedals, controls and
switches on the front panel of the instrument. Same
make and MIDI - for this is the command "set
option, using which you can enable or disable a
of 64 switches, or change the position of one of the 32
regulators. Of course, the handles on the front panel is not
move and no contacts are not closed - we have in mind
logic controllers and switches. However, they produced
actions are absolutely identical and indistinguishable. For 
smooth management controls transmit identical or two bytes of 
data, Depending on the required accuracy.



    Now, using the familiar commands can be written
musical works in the form of successive parcels MIDI.
If the score is normal reserves the musician the freedom of 
interpretation product, then MIDI - musical score is 
unambiguous record of all Action musician with all the nuances 
specific performance. The record, unlike tape - analog, it is 
easy editing, it is easy to change even completely layout

Scores on the instruments or transpose some of the party.


    MIDI-Orchestra.


    MIDI interface is easy to control the whole orchestra of EMR
each of which is pre-configured for a certain
specific individual channel number (1-16) and responds only
to commands transmitted in this channel. For example, a full 
format team to include a note "is as follows:



    1001ssss 0nnnnnnn 0xxxxxxx

  status byte the first byte second byte of data


  where cccc - channel number

      nnnnnnn - note number

      xxxxxxx - keystroke


    So every team is still room information
channel, which allows a single stream of commands transmitted
select teams belonging to different instruments. Modern
EMI have complex algorithms for filtering and processing 
received communications and can operate in several modes.



    The most common mode switches and OMNI
MONO-POLY. When you turn on OMNI tool accepts and executes
team with one, predetermined number of channels - as
monophonic in POLY mode the maximum number of play one
time of vote depends on the specific model of electromagnetic 
radiation. MONO mode used in the parties essentially monophonic 
solo instruments, such as wind, or to simulate the gaming 
equipment by plucking instrument, say, a guitar, where each 
string simulated monophonic melodic synthesizer with

appropriate setting.


    Multitimbral instruments, obtaining in the present
widespread use, can play simultaneously on different
tone, and each timbre behaves as an independent
polyphonic synthesizer with individual parameters and
control. That is a multitimbral instrument can
sounds like a whole orchestra with rhythm section, and 
akkomponementom the solo section. For the independent 
management of these tones they simply assign different MIDI - 
channels. 


    What else is passed to MIDI?


    We have described above some of the so-called channel
messages. There are also system messages and
real-time, do not contain a channel number, and therefore
intended for all devices connected to the system.
Real-time messages are used to control
sequencers, drum machines and other similar devices.
Single-byte command system sync broadcast
uniformly 24 times on the fourth note of the work performed -
it serves to set the tempo and timing. Command "start" and
"Stop" pass every time you start and stop a sequencer or
drum machine and use for remote management.


    From the system message of most interest are
exclusive messages. It is designed for data transmission,
specific for similar instruments - be it dumps
parameters, or samplings of tools in digital form, it is easier
speaking on the MIDI channel can transmit anything, even though
message in ASCII code, just to host the equipment could
correctly recognize and accept the data. Byte of data this
command is the form ID, which released a tool
capable of distinguishing designed it with information from 
"foreign". 


    MIDI-devices.


    MIDI won the music market. Practically no
devices used to perform or record music and do not
familiar with MIDI interface connectors on the rear panel.
Among them are constantly emerging new items, so this review 
does not intended to be comprehensive and should be considered 
primarily as free as, indeed, and all this nonsense about MIDI

Standard ...


    Synth sound produced with both keys, and without them
in the form of e-filling tool. These so-called
tone generator or a musical slang "brains" and are decorated in
buildings, such as "Rack" with standard mounting dimensions
for mounting in a rack. The benefit of the acquisition of such 
tools obvious - instead of multiple keyboards, you can use one

or two, attaching them to a synthesizer via MIDI. Synth sounds
rhythmic instruments also come in one package
"Pads" - the sensitive area to play for them, and without
them - Rack version.


    By performing device with MIDI, are
MIDI-keyboard (the musical slang for "teeth"), pads for
electronic drum kits, special or adapted
loggerhead and wind instruments. Because the interface unleashes
performing and timbral possibilities of instruments,
Musicians who own skills playing on a limited set
tools, get a new set of creativity.


    Sequencers allow you to record, store, edit and
play streams MIDI - messages in real time.
Many sequencers have provided vozmozhnostyamib
studio recorders: multi-track recording, the change
tempo, transposition, editing of a segment
records, etc. Most of them controlled by MIDI. Processing
Sound is produced blocks and sound effects processors
Have MIDI - input for rapid changes in the depth and type of
effect of other parameters during the game. Small Mixing
panels equipped with MIDI, allow us to write all of the
Sound Director and play them with sound works in the
same sequence and strictly synchronously with the soundtrack.
Appeared in a large range of so-called demo-studio
combine in a small case Mixer and 4-h/6-ti
track recorder, also have MIDI control.


    Personal computers equipped with inexpensive card and MIDI
appropriate software can work, such as a sequencer with
excellent service. Interactive editing of scores,
the possibility of its printing, editing sounds of synthesizers 
with visualization of all the envelopes, or sampling from the 
expanse of the wave form a spectrum, make this computer a 
flexible and universal tool for programming the EMR.



    Switches, switches, valves, and synchronizers
Other service devices with no less daunting names
facilitate the work of musicians who have ventured to create a 
large network connected by a MIDI device - MIDI studio. Cost

a studio that fit on the table, much lower than usual, and
most importantly, manage and play all the instruments can
one person.


    Do not think that this high note I end my
research on MIDI. No, do not wait:) But seriously,
I would like to know - it's all anyone is interested?? At
measure instead of thinking on the digitally-theme song I could
tell you about yet more 'madness' and abnormalities ... For 
example of oral-menstrual cycle in programming languages

High-level decisions binomenalno-transcendental
equations of the residents of Far North ...


    Everybody, everybody, I'm going, just do not kick and send 
the letter.