Logic Pro's ability to detect beats by identifying transients in audio material allows you to create groove templates. You can then use these to take the feel of one piece of audio and apply to it to another audio (or MIDI) region.
Although taking your groove from a preformed two- or four-bar loop is possible, it is also likely that your source material will be a full track. The first step in this process then, involves lining it up to the beat and bar lines in Logic Pro, and identifying a region of manageable length (two bars, for example). As in previous tutorials where this process was detailed in Pro Tools (see: Using Beat Detection for Groove Quantizing in Pro Tools) we shall use Stevie Wonder's Superstition as the example source material. There are two clear bars of drums at the beginning'"after a two beat count-in'"that are ideal for this purpose.
Note: you will need to retain regions for all audio that you use a source material for groove templates (you can have as many as you like) in the project that you intend to use them in. There are two ways to approach this:
The planned way: this involves preparing all the groove templates beforehand in a separate project. Keep the regions that relate to each groove template in a folder (pack them into a folder by choosing Folder > Pack Folder from the local Region menu), then save the Project as a template (File > Save as Template'¦). Open the template as the starting point for each project in which you wish to use the Groove Templates.
Starting from a Template project that contain collections of Groove Templates.
The unplanned way: more likely perhaps, is deciding to create and use a Groove Template once a project has begun. In this case, perform all operations on the audio that is the source for the groove either at the very end of the project'"out of the way of the main material, so the tempos don't conflict'"or on an alternative Tempo track. You can select this by going to the Tempo track in Global Tracks and choosing a different tempo track (there are 9) while you create the Groove Template, then switch back to the project tempo track once you are ready to use it. If you have multiple audio sources for multiple groove templates, keep them in a folder as above, and maintain a different tempo track for each one.
Choosing an alternative Tempo Track.
Divide the audio at the start and end of the two-bar section using the scissors tool. Alternatively you could use the marquee tool and select the two-bar section using Shift plus the right and left arrow keys, then click on the selection to create a region.
Drag this region so it starts on a bar line (select '˜Snap to Absolute Value' in the Snap pull-down menu first to make this easier.)
The Snap menu.
Create a two-bar cycle area in the Bar Ruler starting at the same bar line as the selected region. Choose Options > Tempo > Adjust Tempo using Region Length and Locators. In the dialog box that appears, click '˜Globally.'
Finding the tempo of a two-bar loop (note the 2-bar Cycle Area.)
Choose '˜Configure Global Tracks (right-click or control-click on '˜Global Tracks' at the top of the Track List) and tick '˜Tempo' and '˜Beat Mapping.' With the required region selected, click '˜Detect' in the Beat Mapping track header.
Click the plus or minus buttons in the Beat Mapping track header so that all rhythmic nuances of the selected audio region have a transient marker in the Beat Mapping track.
Click the Plus and minus buttons to ensure all subdivisions of the groove are detected.
Why do this, you ask? In previous versions of Logic Pro we would be discussing the '˜Audio to MIDI Groove Template' function in the Sample Editor, but version 9 provides a more straightforward method to create a MIDI region that has MIDI notes at points determined by the transient markers.
How? Choose Convert Regions to New Sampler Track from the Arrange Area's local Audio menu (Control-E if you have the US preset key commands selected.)
In the Convert Regions to New Sampler Track dialog window, click the '˜Transient Markers' radio button and then click OK.
Choose '˜Transient Markers.'
With the new MIDI region created and selected go to the Quantize drop-down menu in the Region Parameters section of the Inspector. Click the disclosure triangle and choose Make Groove Template from the list that appears.
The name of the groove template will be the same as the region selected, which should also be the same as the original audio region.
Click here to select Make Groove Template.
Applying the template to MIDI is as simple as selecting the MIDI region then choosing the groove template from the drop down Quantize list in the Region parameters area. Applying the template to an audio region requires that you do one of two things:
Option 1 most clearly resembles what happens when using Beat Detective in ProTools to perform this operation, so we will use that method. Option 2 will form the subject of a future article.
The target audio should be lined up with Logic's Bars and Beats grid as far as possible. Depending on your working methods you will either be dealing with shorter sections, the start of which are lined up with the bar line (perhaps by creating a tempo map), or one long performance at a steady tempo, for example drums recorded to a click track. It is certainly easier to perform some of the following steps if you are dealing with smaller sections. Again two or four bars are ideal.
Detect the transients of the target material as before (note that Apple Loops will already have their transients detected, these will show up in the Beat Mapping track.)
Divide the target audio at transients. This is an option only found in the Key Commands, so you'll need to assign a key command to it if you haven't already done so.
Target audio region divided at transients (shown in the Beat Mapping track).
Next, open the Event List: you will see the individual regions selected there. From the Event List's drop-down Quantize menu, find the Groove Template you created and choose it.
Applying the Groove Template in the Event List.
From the local menu, and with the regions still selected choose Region > Trim Region End to Next Region.
Trimming the region ends to the next region.
Listen for any unwanted audio revealed by this operation.
If you would like to add crossfades at each region boundary then, with the regions still selected, go to the Region parameters box in the Inspector, change the Fade type from '˜Out' to '˜Crossfade', then move your cursor slightly to the right and click-drag the value upwards to something like 30.
Choosing '˜X-fade' in the Region parameters.
Crossfades added at all region boundaries.
Learn more about Logic Pro with these tutorials.