Logic provides two ways to filter MIDI input. Using the Song Settings window's MIDI pane, you can filter out incoming MIDI events such as note events, program changes, pitch bend data, and aftertouch information. Additionally, you can also adjust quantization as you record MIDI events into Logic using the MIDI Thru feature. The following section details both techniques.
Using Input Filtering
MIDI controllers can generate a variety of MIDI commands. In addition to note-on and note-off information, they also send information like continuous control numbers and aftertouch (pressure) commands. In some cases, you may not want to record every type of information that your controller is generating. For example, you may not want to record aftertouch information if you have a sound that reacts strangely to aftertouch and you sometimes inadvertently press too hard on the keys. You can use input filtering to prevent this information from getting to the track.
Choose File > Song Settings > MIDI. The Song Settings window opens to display the MIDI pane. By default, the General tab is displayed.
From the Song Settings window's MIDI pane, select the Input Filter tab.
Select the Notes check box, and play the keyboard. You don't hear anything, because you've filtered all incoming note messages so that they never make it into Logic's sequencer.
Make sure you have the Drum Kits track selected in the Arrange window.
Click the Notes check box to deselect it; then play your MIDI controller keyboard.
There is sound again. Take note of the other input filter optionsthey are here when you need them.
Close the Song Settings window.
Using MIDI Thru Filtering
MIDI Thru filtering adjusts quantization as MIDI events are recorded into Logic. This ensures that notes conform to perfect rhythmic positions on Logic's time grid and can really help to clean up loose playing as you record. Let's try it out.
Click the background of the Arrange window to ensure no MIDI Regions or Audio Regions are selected.
With nothing selected in the Arrange window, the Region Parameter box updates to say MIDI Thru, and you are now in MIDI Thru mode.
From the Region Parameter box's Quantize menu, choose 1/2-Note. The 1/2-Note setting will hard-quantize all input events to half notesthat's two notes per bar. This is a very obvious quantization, so it works well for the next experiment.
Select an empty MIDI track (we selected the Audio Instrument track named Inst 3).
This next step is just for experimenting with MIDI Thru, so it's fine to record to an empty track. You will delete the newly recorded sequence in a few steps, so don't worry about adding sounds to the song.
Press the Record button (or press * on your keyboard's number pad) and begin recording.
Play MIDI events very rapidly on your controller keyboard so that you create a lot of MIDI notes.
Double-click the newly recorded sequence to open it in the Matrix Editor. All of the input notes have been quantized to 1/2-Note.
Close the Matrix Editor.
Delete the newly recorded MIDI Region.
Set the MIDI Thru quantization to Off.