Our test case is a snippet from a metalcore band I've been working with. The band has good material, but was not comfortable tracking to a metronome. In order to get the super-precise timing expected for this genre, we'll need to do two things: First, create a tempo map that will allow us to do some grid editing; and second, use the magic of digital audio to correct as many timing errors as we can.
I'll be explaining this process in Pro Tools, but most major DAWs will have similar features.
Creating a Tempo Map
1. Select all the drum tracks, and create an edit/mix group. To do this, click on the “groups” panel in the lower left corner, select “New Group,” and select the tracks you want to include. This step is absolutely crucial to avoid changing the phase relationships between the different microphones.
2. Since this song was not recorded to a click track, we now need to create a click track that adheres to the ebbs and flows of the original performance. This isn't quite as hard as it sounds, but it does take some time. Making sure that the “Tab to Transients” function is enabled, we're now going to look for drum hits spaced about two measures apart that seem to be directly on the beat. These will be our anchor points for creating the tempo map. When I find a good candidate, I will tab to the transient, and then separate the region using Ctrl+E (Command+E for Mac). (Make sure you have your edit group enabled, to apply the separation across all the drum tracks.)
3. Here's where the magic happens. Using the Identify Beat command (Ctrl+I Windows/Command+I Mac), we're going to tell Pro Tools where to place the beats. Let's consider the first kick hit to be beat one of bar one, and the second selected kick hit to be the “and” of beat four of bar two. We'll input these values into the Identify Beat tool, and Pro Tools will automatically calculate the tempo of the region. (A handy tip: You'll be working in ticks, and you'll need to know that there are 960 ticks to a quarter note. Thus, an eighth note would be 480 ticks, a sixteenth note 240, etc.)
4. Now, we'll follow this same procedure for each new region, telling Pro Tools on which beat each region starts and ends. Unless you're doing drum tracks for an AC/DC cover band, you'll probably have to bust out those counting skills to correctly identify syncopation. You can check your work by creating a click track (Track>Create Click Track), and listening to see if the calculated tempo bears any resemblance to the tempo of the recorded performance. After a while, you'll develop an ear for it.
5. Once we've completed the tempo map for the session, the only thing left to do before moving on to timing is to select all of the regions, and use Ctrl+H (Command+H for Mac) to heal the separations we created in the regions.
A quick note here . . . in audio land, discretion is often the better part of valor. Just because you can process something doesn't for one second mean that you should. (See the previous article where I talk a little bit about the pros and cons of corrective editing.) However, the hardcore/metal genre usually favors extremely precise, consistent drums, and it's our job to give the client what he or she wants. So here we go . . .
1. Enable Elastic Audio. I've had good luck using the “Polyphonic” algorithm on the past couple of tracks, but use your ears to tell you what sounds best for your track.
2. Making sure your drum edit group is still active, put the drum tracks into “Warp” view. The tracks should go gray.
3. We're going to work in two-measure increments, but before starting, we're going to create a warp marker on the hit after the section we'll be working on. This prevents us from accidentally throwing the whole track out of time. To create a warp marker, simply click on the vertical gray line that represents a transient. It will go black.
4. Using the selector tool, select a region that includes all of the hits you want to work with (i.e. the first two measures).
5. Now we're going to use the Quantize function (Alt+0 Windows/Option+Alt Mac) to analyze and quantize the audio. Notice that I've set the grid to an 8th-note value (to catch the syncopation of the last beat) and told Pro Tools to exclude hits within 6% of “perfect.” I've also set the “strength” of the quantization to 94%. I've found that this gives very good results without sounding too robotic, but as always, use your ears.
6. After applying the quantization, here's what Pro Tools has given me.
I'll listen for false triggers and other electronic glitches (hear 'em?), and make any necessary manual adjustments. (Another handy tip: To remove a warp marker, just Alt-click/Option-click it.) After that, I just repeat the process, section by section. Tricky drum fills may require special attention, including changing the grid values, or even just selecting each hit in the fill and aligning them all by hand. This is slow going at first, but after a few dozen bars you'll be moving along.
And Finally . . .
After all that editing, we hit the fun part: Mixing. Here's our end result, using the drum bus techniques I outlined in "How to Mix Drums in 60 Seconds," sneaking in some sample layering (layering, not replacement), and adding a touch of reverb.
That art history degree is starting to look pretty good, huh?