Map MIDI controller knobs to plug-in parameters

When you play a software instrument with your MIDI controller keyboard, you can modulate the sound with the pitch bend wheel or the mod wheel (the mod wheel generally controls a vibrato or tremolo effect).

If you want your performance to be even more expressive, you can map knobs or faders on your MIDI controller to software instrument or effect plug-ins in Logic Pro. 

In this tutorial, you'll assign a knob from your controller to the frequency parameter of an effect plug-in, the Ringshifter. You will then play notes on the keyboard while tweaking the knob to warp the frequency spectrum of the synthesizer you're playing. 

1. Choose a patch and add the Ringshifter plug-in

To get started, you will create a new project with one software instrument track, load a patch, and add the ring modulator plug-in.

1. Choose File > New to create a new empty project.
2. Create one software instrument track with an empty channel strip.
   
3. In the Library, choose Synthesizer > Lead > Festival Lead.
4. Play a few notes to play the synth.
5. On the Festival Lead channel strip, in the Audio FX section, click below the last plug-in (St-Delay), and in the plug-in pop-up menu, choose Modulation > Ringshifter.
6. Play a few notes while you drag the Frequency knob up and down in the Ringshifter.
   

Now that you hear how the Frequency knob lets you shift the frequency spectrum of the synth sound, you will assign that knob to a physical knob on your MIDI controller. Let's unleash the fun!

2. Map a Smart Control to the plug-in knob

The Smart Controls pane displays knobs that give you access to key plug-in parameters for the selected track. In this exercice, you'll map a Smart Control knob to the Frequency knob in the Ringhshifter. 

1. Choose View > Show Smart Controls (or press B) to open the Smart Controls pane.
2. In the Smart Controls pane, click the Inspector button (top left).
   
3. Click the first knob in the Smart Controls pane to select it (the knob is framed in blue).
4. In the Inspector, in the Parameter Mapping area, click the Learn button.
   
5. In the Ringshifter, tweak the big Frequency knob.
   That's it! The selected Smart Control knob is now mapped to the Frequency knob in Ringshifter.
   

In the Smart Control pane, you can now drag the FREQUENCY knob to remotely control the Ringshifter's Frequency knob.

3. Assign a MIDI controller knob to the Smart Control

Finally, let's assign a physical knob on your MIDI controller to that FREQUENCY Smart Control. 

1. In the External Assignments area, click the Learn button.
   
2. Make sure the FREQUENCY Smart Control knob is highlighted in red.
3. On your MIDI Controller, turn a knob.
   That knob now remote controls the FREQUENCY Smart Control knob.
4. In the External Assignments, click the Learn button to turn it off.
5. Close the Smart Control pane.

Now play the keys while you turn the knob on your keyboard to shift the frequencies of the synthesizer.

You can map and assign Smart Control knobs to any parameters of software instrument or effect plug-ins in Logic Pro, including 3rd party plug-ins. Repeat this procedure to assign more knobs to different plug-in parameters and manipulate various aspects of the sound at the same time.