"Lectures in Beginning MIDI," part 2

Sequencer?

Mr. MIDI


Musical instrument manufacturers around the world got together and reached an agreement that provides a standard way of turning music into digital information, recording it, and playing back music from the recorded data. In the first lecture, we explained that this is what MIDI is. I suppose you could think of MIDI data as a sort of powered-up version of printed music.

Let's take a quick look at what MIDI data looks like. The pitch of a note is recorded as the location of the note; i.e., the number of the key (counting from the left side of the keyboard). Middle C on the keyboard is 60, the C-sharp that's one semitone above that is 61, and the D note is 62, etc. ontei

So, let's suppose you played this middle C note. The moment that you press the note, a piece of information saying "a note has been played -- turn on the sound!" is transmitted. (This is called a Note On message.) Since a switch on/off movement can be expressed as 0 or 1, it's easy to convey this information as a number.

Then comes information telling that the key that you pressed was note number 60.
Finally, a sensor built into the keyboard detects how strongly (quickly) the note was pressed, and this is converted into a data value of 1--127 (127 steps). (This is called the "velocity." Higher numbers mean that the note was played more strongly.

on_off
  • Play a note! (On)-Note pitch-Strength

    Then, the instant you release the note,

    Stop the sound! (Off)-Note pitch-Strength (The speed at which you released the key.)

    is transmitted.

This is the data that's created when you press and release one note. Make a lot of these ... and you might get some music!



This data can be recorded in time by keeping track of which note was played (or released) how strongly at what time. And since all of this data consists of numbers, we can use a computer to keep track of it! That's what "sequencers" are -- dedicated hardware or personal computer software that does exactly that.

MUSIC SEQUENCE SOFTWARE

XGworks
MUSIC SEQUENCER

QY700
"Sequencers" are used for recording, but that doesn't mean that you have to play in order to record! All you have to do is record the note data at the appropriate locations on the time line, and there are various ways to do this, such as pasting note symbols onto a staff displayed in the screen, or by typing in numbers, etc.

Input


Of course, there's no point to this if all you can do is record! Sequencers are only useful when they playback the data that was recorded. It goes without saying that all sequencers are able to playback the recorded data at the appropriate times for each note. But this data (MIDI data) doesn't make the sound itself. You need a device that receives the MIDI data that comes from the sequencer, interprets this data, and produces an actual sound. These devices are called MIDI sound modules or tone generators. Synthesizers, samplers, drum machines, and electric pianos are examples of such devices.

MIDI equipment


Author: Shouichi Karasaki (Kamonegi House)

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