MIDI Protocol in Logic Pro X
The MIDI (Musical Instrument Digital Interface) protocol enables compatible devices to send and receive data. It was created to allow hardware to speak to each other. Logic Pro uses the MIDI protocol to play and record software instruments, automation, and external MIDI hardware.
MIDI does not contain audio. Your external MIDI devices still need their audio to be routed into your computer and Logic Pro to be heard.
Sending MIDI messages
MIDI messages are sent from one device and received by another, such as from a MIDI controller to Logic Pro. These messages can include information about pitch, velocity, sustain, and much more. Logic Pro translates the MIDI messages and sends them to a software instrument or to external hardware.
You’ll use MIDI to accomplish many of your musical goals in Logic Pro. You can even assign your MIDI controller to a Logic Pro command. It’s not difficult to map a button on your MIDI keyboard to tell Logic Pro to play your project. But while Logic Pro is always using MIDI under the hood, you’ll mostly be using MIDI to play software instruments.
To verify that Logic Pro is receiving the messages your MIDI controller is sending, show the MIDI activity in the LCD on your control bar as follows:
Control-click an empty area on your control bar and choose Customize Control Bar and Display.
A window opens with customization options.
In the LCD column, choose Custom.
Select the MIDI Activity (In/Out) check box.
Click the OK button.
Your LCD displays a small dot in the upper-right corner . If no MIDI is being received, the display will read No In/No Out.
Changing MIDI channels
MIDI devices send and receive information on 16 different channels. Many Logic Pro software instruments are multi-timbral, which means they can play multiple different sounds simultaneously. You can set these sounds to different MIDI channels, which allows you to play them independently using multiple MIDI controllers.
Or if you have a MIDI controller that has a split or layer function, you can potentially use a single keyboard to play multiple software instruments at a time.