The midi connection, Audio – Apple Logic Pro 8 Getting Started User Manual
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Appendix A
Audio and MIDI Basics
The MIDI Connection
MIDI, as mentioned, is also a hardware “interface” which consists of a standardized set
of connectors labeled IN, OUT, and THRU.
MIDI connectors consist of a round socket with five holes arranged in a semicircle. MIDI
cables, used for connecting MIDI devices, have a matching plug that features five pins.
Only three of the pins actually carry information.
MIDI only works in one direction on each connector. If you want your MIDI keyboard to
send messages to, and receive messages from Logic, you must connect two cables.
Here’s the way your MIDI connections must be made, in order to work:
 MIDI OUT sockets must be connected to MIDI IN sockets on the receiving device.
 MIDI IN sockets must be connected to MIDI OUT sockets.
The MIDI THRU connector is not found on all MIDI devices. It simply mirrors the MIDI
messages arriving at the MIDI IN socket, and allows you to “daisy-chain” more MIDI
devices.
MIDI messages are sent from a MIDI controller such as a keyboard or sequencer—such
as Logic—via the MIDI OUT connector. The device (MIDI synthesizer or sound module)
receiving the MIDI messages at its MIDI IN socket, responds to these messages by
playing sounds.
Important:
Remember, MIDI does not send sounds. It sends instructions on how, what
and when to play.
Audio
Audio, as a term, basically refers to any sound that you can hear. In the physical, as
opposed to computer world, this is known as analog audio. When Logic records analog
audio signals via an audio interface connected to, or installed in, your computer, the
audio is converted into digital information. This information is stored as a digital audio
file on your computer hard disk.
As with MIDI, the digital part sounds technical, but really isn’t. As discussed earlier,
computers talk digitally, and need to deal with analog audio signals as digital
information.
Important:
Unlike MIDI, digital audio files are actually recordings of sounds, not an
instruction language.