Apple Logic Pro 9 - Manual (Page 467)

3 Select the checkboxes that correspond to the MIDI event types you would like to filter at
the Logic Pro sequencer input.
Turning MIDI Thru Off When Recording
When an External MIDI instrument track is selected in the Arrange area, its Record Enable
button is automatically turned on, and the instrument will pass events through the
computer (MIDI Thru function). You can turn off the MIDI Thru function by deactivating
the Record Enable button.
However, there are situations where you may want to record to a track that is not
automatically routed to a MIDI port, such as when you are performing a system exclusive
(SysEx) dump from a device. Although many MIDI devices require a bidirectional—in and
out—MIDI connection to allow this type of communication, some devices react strangely
to incoming data, sent from Logic Pro’s MIDI Thru function. This can result in loss of data,
devices not responding, and other unexpected behaviors.
If you want to record a memory dump from a device that is problematic when connected
bidirectionally, disable the instrument’s MIDI Thru function.
To assign an instrument with a permanently disabled MIDI Thru function
1 Open the MIDI project settings by doing one of the following:
• Choose File > Project Settings > MIDI.
• Click the Settings button in the Arrange toolbar, and choose MIDI from the pop-up
menu.
2 Click the General tab.
467 Chapter 14 Recording in Logic Pro