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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 used to work
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 music 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.
Digital Audio
Digital 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.
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.
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