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Automating Plugins in Logic Pro 7

Applying a chorus effect only to specific sections within an audio track By Frank Moldstad

Logic Pro 7's Chorus plugin
One of the best things about mixing audio tracks in a computer is the ease with which parameters such as volume and panning can be automated. Automation can be set up for multiple tracks simultaneously, to add power to a songs bridge, or emphasize specific instruments in another section.

But one of the most dramatic uses for automation is to vary the intensity of effects such as reverb or chorus. In Apples Logic Pro 7, all mix functions can be automated, including plugin and virtual instrument parameters. As this tutorial will show, automating plugin behavior is easy and well worth the effort. The task is to automate a Chorus plugins intensity on a guitar track, causing it to rise and fall in specific places. Audio clips are provided at the end with before and after examples.

The guitar track was recorded as part of a multitrack project that included drums, bass, multiple vocals, keyboards and other guitars. As the rhythm guitar, its the bedrock of the song, playing continually from start to finish. Throughout the verses, it alternates between punctuated staccato chords and an arpeggiated chordal section. I decided to contrast these two parts by adding a chorus effect on only the arpeggiated chords.

First, I chose the effect and inserted it on the guitar track. I used the Chorus plugin that comes with Logic Pro 7, and selected one of its presets, called Mega Wide Chorus. This provided the airy, harplike sound that I had in mind for drawing out the guitars arpeggiated chords. I adjusted the intensity from the default 89 percent to 40 percent to make it more appropriate for the track.

The next step was to enable the tracks automation display. This process is the same for automating faders, panning or plugins -- select View>Track Automation in Logics Arrange window (Image 1).

Image 1

When I did this, a horizontal yellow envelope line appeared on the track, for volume automation (Image 2).

Image 2

To switch to the Chorus automation, I went to the drop down menu in the track header and selected Chorus>Intensity (Image 3). Other automatable parameters were Mix and Speed.

Image 3

A new envelope line appeared on the track, this one green. By default, it was set to 10 percent (Image 4).

Image 4

Next, I zeroed in on the arpeggiated section where I wanted the Chorus effect to be. I added two nodes at this point. Nodes are handles for raising or lowering the envelope, and they are added by clicking once with the mouse on the envelope line. The first node I lowered to zero, and the second I raised to 40 percent, which is the intensity that I wanted (Image 5). Then I went to the very beginning of the track and lowered the node there to zero.

Image 5

At the end of the arpeggiated section, I added two more nodes, setting the first one to 40 percent and the second one to zero. But this was a tight spot, because the staccato chords began almost immediately afterwards, and I didnt want the chorus effect on them. So I zoomed into the track nearly to the sample level and found the precise moment when the arpeggiated chords stopped and the staccato chords started. I positioned the nodes to turn off the chorus immediately there (Image 6). 

Image 6

Then I zoomed back out to see the final envelope, which looked like this.

Final envelope

Below are two short MP3 clips, one without the chorus and one with it. For contrast, each clip has two of the short staccato chords leading into the arpeggiated section.

Arpeggiated Chords Without Chorus:


Arpeggiated Chords With Chorus:


After listening to the automated chorus effect in the context of all the other tracks, I was happy with the result. It made the arpeggiated chords stand out nicely against the rest of the rhythm track, and created an interesting new dimension in the song. Satisfied that it worked, I went through all three verses and created an automated envelope everywhere the arpeggiated guitar section played.

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Related Keywords:Apple, Logic Pro 7, plugin, automation, mixing, chorus, envelope, volume, panning


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