The EM Poll

Drum Replacement Primer

Nov 1, 2006 12:00 PM, By Alec Tabak

           

FIG. 1: In the Pro Tools AudioSuite plug-in Sound Replacer, you can see that three different snare drum samples are assigned to corresponding threshold levels. Notice that a rim shot sample is assigned to the highest threshold.

Imagine that you have finished tracking your latest project, and the time has come to mix. You've got the vocals sounding clear and lively, the guitar and bass tones are just right, but no amount of processing makes the drums sound like you want them to. Although the drummer's performance was fine, you might be wishing you had captured it differently. Wouldn't it be great if you could change the drum sounds without rerecording the track?

Drum replacement, a technique that Roger Nichols pioneered in the studio with Steely Dan in the late '70s, has long helped engineers and producers fix problem drum tracks in pro studios (see the sidebar “Meet Wendel”). Drum replacement is invaluable when your original choice of drums and miking techniques leaves you with sounds that don't quite fit the final mix.

The idea of drum replacement is to double, or sometimes replace, a subpar drum track using a second track of high-quality samples. In this introduction, I'll show you how to replace kick and snare tracks manually, semiautomatically with MIDI, and with an automatic replacer plug-in. Although the kick and snare aren't the only replaceable drums in the kit, their sounds are often the most prominent in mixes: replacing these drums is often enough to bring the rest of a drum mix in line.

Like any fix-it-in-the-mix technique, drum replacement is more time-consuming than recording the instruments right the first time, and some problems are just too big for it. Nonetheless, the following tools and techniques are worth learning to use, particularly if the physical limitations of your personal studio make drums tough to record well.

Replacement Done Right

A natural sound is the hallmark of successful drum replacement. No one who listens to your song should be able to tell you've replaced the drums. That means you must retain a part's groove and the dynamics of the drummer's performance. The simpler the drum part is dynamically and rhythmically, the easier drum replacement is to perform. However, even somewhat intricate parts may be replaced using the right tools and a little patience.

Your replacement track must blend seamlessly with the other tracks in your drum mix: each drum sample should sound like it was part of the drummer's original kit. The best way to do this is to combine the original and replacement drum audio in the final mix. This reinforcement approach preserves some of the leakage that is characteristic of live drum recording and often helps replacement tracks sound natural.

For the purpose of drum replacement, all drum sounds have two basic elements. First, there is the attack transient produced by the drummer's stick or bass drum beater striking the head. Second, a resonant tone with sustain and decay characteristics follows the transient. The volume peak can coincide with the transient or it can be part of the tone, depending on the type of drum, hit, and recording method.

The first step in drum replacement is choosing the right replacement sounds. These may come from your own sessions or a drum sample library. Whatever the source, your replacement kick and snare should complement the tracks you want to replace, particularly if you adopt the reinforcement approach. Solo the kick or snare track, listen to it along with the rest of the drum mix, and then listen to it in the context of the main mix.

Focus on what you got right when tracking the drums. Do individual hits come through sharply? If so, select a replacement sample that enhances the drum tone and doesn't have too sharp a transient. Does your kick or snare sound good when you solo it but fail to cut through the main mix? In this case, the best replacement sample will have a sharp attack but will decay rapidly. If neither the attack nor the decay of your drum track sounds good to you, select a replacement sample that has it all, but try to use some of your original track to keep things sounding natural.

Kick and Snare Characteristics

Kick drums and the sounds they produce vary widely between different musical genres. A jazz drummer's kick may be tuned as high as a rock drummer's rack tom and sustain as long; a heavy-metal drummer's kick is sometimes heavily dampened and tuned so low that the sound is not much more than a transient with zero sustain.

Typically, the attack transient of a kick drum has a frequency range between 2.5 and 6 kHz, while the tone may range anywhere from 50 to 100 Hz. The tone's decay time can range from 15 ms to several seconds.

Two aspects of kick drums merit special attention in drum replacement. First, hard kick hits are slightly brighter than soft ones. If the drummer's kick dynamics vary, you'll need two or more replacement samples that reflect the timbral differences that harder hits produce. Second, the kick drum in a song almost always has a special relationship with the bass instrument. Whether the kick and bass lock into a single groove or are relatively syncopated, the interaction of these instruments' frequencies is critical. Choose replacement kicks that complement the song's bass parts and tone.

In pop and rock songs, the snare drum regularly forms the centerpiece of the drum part. Whether the drummer plays a simple two-four backbeat or a more complex pattern, the sound of the snare may be the most prominent and distinctive part of your drum mix. While snare sounds vary as widely as kick sounds, the frequency range of snare transients is narrower, tending to fall between 4.5 and 5.5 kHz. The snare's fundamental tone can be anywhere from 100 to 300 Hz, but most of the snap and sizzle is above 6 kHz.

Drummers hit the snare drum in several different ways. Each hit has a unique sound, which your replacements should mirror. If the drummer plays a rim shot, for example, your replacement sound should be a rim shot as well (see Fig. 1). A snare's timbre may become brighter as it's hit harder, but not as much as a kick drum's.

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