Capturing the Arpeggiator Output in Logic Pro X

One of the most impressive improvements in Logic Pro X is the addition of MIDI FX plug-ins, in particular the Arpeggiator. In this tutorial Darren Burgos reveals two ways to capture its actual output.  

Logic's new MIDI FX Arpeggiator can add instant complexity to sustained chords, and even single notes. Based on the parameters you set, it can play notes in sequence up, down, up and down, across multiple octaves, and much more. When you go to record the arpeggio, it's a bit of a let down though. The actual notes it creates are not directly recorded, only your held chords or single notes. In this article I'll show you two ways of capturing the output of the arpeggiator. One method is actually built right into the arpeggiator itself! Let's get started.

First we'll explore how to use the Arpeggiator's MIDI Drag feature:

Step 1 - Add the Arpeggiator to a Software Instrument

Open a new Empty Project in Logic, and choose the ESP synth (the Setting “Fat Square Bass” should work well with the Arpeggiator), then add the MIDI FX Arpeggiator to the channel strip. Hold a chord down and watch the small icon that looks like steps in the top left corner. Now release the chord. When you're holding a chord down, the icon is “lit up.” This is a MIDI drag! Basically whatever pattern Arpeggiator creates, you can drag it out and into the Workspace/Arrange area. 

add to software instrument

Step 2 - Drag the Pattern to the Track

Hold a simple three note chord down with one hand, and with your other free hand click the icon with your mouse/trackpad and drag it to the track in the workspace. There's your arpeggiation! Now you might be wondering why it's such a small slice, but remember what the arpeggiator is actually doing… it's repeating the chord by playing the individual notes in sequence over and over again. 

drag pattern to track

Step 3 - Loop the Regions 

To play the arpeggiation for as long as you intended, simply loop the region for as many bars as necessary. Repeat this process for all the chords in your progression/song and you'll in effect, have built a note for note MIDI version of Arpeggiator's output.

Loop the regions

Step 4 - Bypass Arpeggiator

Remove or Bypass Arpeggiator now, since you're done with it! If you don't, the MIDI regions you've dragged will re-trigger Arpeggiator.

Step 5 - Tips for Using MIDI Drag

Keep in mind, when you're dragging out multiple arpeggios, position your mouse onto the next unoccupied bar. Arpeggiator's MIDI drag places its patterns on the start of a bar only. If say the patterns you're dragging are a half bar in length, and you position the second pattern in the middle of a bar, you'll overlap the dragged region onto the first.

Pic 4

In the steps above, we simply used the default arpeggiation, but feel free to change any parameter on the arpeggiator… MIDI drag will work with any pattern Arpeggiator creates. For example the default pattern simply plays 16th notes starting from the low note to the high note, if we change Arpeggiator to a more complex pattern like up and down, with an octave range of 4, the pattern you drag will be longer.

pic 5

Use the Mac's IAC Driver to Capture MIDI:

OK, so now we know we can manually piece the Arpeggiator together with the drag button, but what about simply capturing the output of an already built chord structure, or for that matter, any MIDI FX output (not just Arpeggiator)? Since Logic doesn't yet allows for this, we'll need to use the Mac's built-in Inter-Application Communication driver, or IAC driver for short. This gives us a virtual path to first send Arpeggiator out of Logic, then back through as MIDI that Logic can then capture. Logic see's the IAC driver at its physical input just like it sees any incoming MIDI controller. Virtual or physical, Logic can't tell the difference.

Step 1 - Enable the IAC Driver

First, we'll need to enable the IAC driver. You only have to do this once, as your Mac will remember this through restarts and shutdowns. Go to the Mac's Finder, click on the Go Menu and select Utilities. Open the application called Audio MIDI Setup. By default, only the audio side of audio/MIDI appears. Click on the Window menu, then onto Show MIDI Window. Double-click the IAC Driver icon in the window that appears. Make sure the “Device is online” checkbox is enabled, then close the window and Audio MIDI Setup. Now that we've enabled the virtual path, let's go back to Logic.

Enable the IAC driver

Step 2 - Duplicate the Track & Change to External Instrument

Duplicate the channel strip with the arpeggiator you want to capture. Click the New Track With Duplicate Setting Button. Change the instrument of the duplicated track from ESP (or whatever synth you used) to “External Instrument” by clicking and holding, and then selecting it. By using the External instrument, we'll be able to send Arpeggiator's MIDI out of Logic. Click on the External Instrument to open it. from its MIDI Destination menu, select IAC Driver, then close its window.

duplicate track

Step 3 - Move the MIDI to the External Instrument Track

Now, move the MIDI from the original Arpeggiator track down to the duplicated External Instrument track. This is an important step. Your original chord progression on the intended instrument will be used to trigger the duplicated Arpeggiator. This duplicated Arpeggiator sends the arp pattern to the External Instrument, that is then sending its output to the IAC driver! It's actually a lot simpler than it sounds!


Step 4 - Record Arpeggiator's Output

We're nearly there. Click back onto the original track, and bypass the Arpeggiator since you'll no longer need it. There should be no MIDI here since you've moved it down to the duplicated External Instrument track. Make sure the “R” button is enabled, position the timeline at the start of the progression (that is now on the duplicated track) and start recording! Allow it to play all the way through… as it records, you should see the individual notes being captured.

Record the arp's output

Step 5 - Tips

Once captured, you should immediately bypass the External Instrument and it's Arpeggiator since it's output will continue to send even when the track is muted! Depending on the speed of your Mac, how complex the song your working in is, and other factors, you might have to quantize the resulting captured MIDI. As I mentioned briefly above, this is also a great way to capture MIDI from any of the other MIDI FX plug-ins like Modulator, Note Repeater and Randomizer.

Hope you enjoyed this article, and thanks for reading it!

Darren started making music on computers when he was a teenager in 1987. His first computer was an Amiga, and when he realized the power of computer-based production, his addiction for making electronic music began. Darren switched to Mac in 1994 and started using Logic Pro. He's been involved in many music projects over the years incl... Read More


Great article - thanks! Well-explained and very useful.
This opens up tons of possibilities…..
Yes indeed a great help for me too. I used this all the time in the old logic's environment window.
I've noticed that unfortunately in the controller section of the midi plug-ins Logic developers have skipped a number of available midi controllers, between 31 and 64 for instance. I need those however, since I'm working on third party self developed instruments that have their controller range in this zone.
Is there a reason for doing so? and is there a chance that this will be rectified in later versions? Is there a way to bypass the problem?
After reading the brilliant article by Darren, I guess he's the man of the solution.
Thanks for the article. Very useful.

I wonder if it would be possible to capture multiple tracks simultaneously this way?

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