Reference Guide

57
Computers, sound and music
Introduction
The MIDI language conveys information and instructions, both from the computer to the instrument
and from the instrument to the computer. For example, if your computer wants your keyboard to play
a note, it sends a MIDI “Note On” message and tells the keyboard which note to play. When your
computer wants the keyboard to stop playing that note, it sends another message that stops the note
from playing.
The MIDI language has many other instructions, such as messages to change the sound that is
used to play the notes (the bank and patch), messages that enable working with the sustain pedal
and the pitch-bend wheel, and others. By sending the right messages at the right times, your
computer can control your electronic instrument and make it play music.
MIDI information can be sent on 16 different channels. You can set up your MIDI equipment to listen
for messages on all channels or on only a few.
MIDI files contain all the MIDI messages and timing information that are needed to play a song. MIDI
files can be read and played by many different programs, including SONAR, and can even be played
by programs on other types of computers. MIDI files have the extension .mid.
There are several important advantages of the MIDI format:
• Large amounts of music can be stored in a very compact form
• Different parts of a piece can easily be assigned to any instrument you can imagine
• The music contains information on notes, tempos, and key signatures that makes it possible to
display and edit the piece using standard musical notation
The primary disadvantage of MIDI is that the quality of the sound a listener hears will vary depending
on the MIDI equipment the listener is using. For example, MIDI usually sounds much better on an
expensive synthesizer than it does on an inexpensive sound card.
Next topic: “Digital audio” on page 57.
Digital audio
Digital audio (frequently referred to here as just “audio”) is a simple way to record and play sounds of
any type. It works like a tape recorder—you record something, then later play it back. Digital audio
stores the sound as a long series of numbers. To record audio in SONAR, you have to have an audio
cable connecting the audio output of your electronic instrument to the audio input on your sound
card or audio hardware. If you’re recording vocals or an acoustic instrument, you need to connect a
microphone to the audio input on your sound card or audio hardware.
Sound Waves
Sound waves are vibrations in the air. Sound waves are generated by anything that vibrates; a
vibrating object causes the air next to it to vibrate, and the vibration is passed through the air in all
directions. When the vibrating air enters your ear, it makes your eardrum vibrate, and you hear a
sound. Likewise, if the vibrating air hits a microphone, it causes the microphone to vibrate and send
electrical signals to whatever it's connected to.
These vibrations are very fast. The slowest vibration frequency you can hear is about 20 vibrations
per second, and the fastest is around 16,000 to 20,000 vibrations per second.