You May Ask Yourself…
Does a track need compression? Sometimes, a wide dynamic range can deliver the absolute perfect expression for a part. Crush that signal down, and something beautiful may be lost. Always listen critically and make processing decisions that truly improve musical communication and impact. There is no “have to” in music production, so don’t compress a signal simply for the sake of compressing it, or because you read somewhere that electric-bass tracks should always be compressed, or some other such nonsense. Always find an explicit purpose for inviting compression to the party.
Diving for Dynamics
Ready to dig in? Experimentation is half the fun of signal processing, so don’t be afraid to break rules, jump into the abyss, or do something another creator might consider irrational or just plain dumb. If you get to something that blows your mind, document the settings for your home-studio trick bag, but remember—just because something worked on a particular instrument in a specific mix at a certain time, does not mean it’s going to always provide the exact same sound on a different day. That volatile unpredictability in the studio—often caused by almost imperceptible changes in gear settings, or the performance idiosyncrasies of different artists, or the distinctive sonic signatures of various instruments, or perhaps even the position of the moon on certain nights—can serve to fire up your creativity. If you let it. Always be ready to accept the “surprise gifts” that drop into your lap as you’re chasing sounds.
Whether you eventually toss out convention or not, however, it helps to start out with some basic case studies so you’re not working completely in a web of oblivion. Here are some very rudimentary settings to get you on your way.
Vocals. Typically, you want a lead vocal beautifully upfront and soaring over the instrumental track to ensure lyrical intelligibility—and the artist’s emotional expression—impacts listeners. However, there isn’t a magic compression setting that works for all singers and all styles. There’s simply too much dynamic diversity between vocal techniques, the vocal arrangement (loud and soft passages), different stylists (rock, jazz, rap, etc.), and even the music track (some musical sections may be interfering with hearing the vocal clearly more than others). To get a vocal upfront, try starting with a -9dB threshold, a 2:1 ratio, an attack time of 1ms or less, and a release time of approximately 50ms.
Electric Guitar. Overdriven and distorted guitars already have some compression in effect, due to the nature of saturation—whether the grind is from a tube or solid-state amp, a stompbox, or a digital emulation. But guitars still need to present right in your face—even when clean toned—so try these settings to get the party started: threshold at -3dB, ratio between 2:1 and 4:1, attack at around 25ms, and release set at about 200ms.
Acoustic Guitar. Getting fingerpicked, single-note melodies to appear smooth and balanced may require compression, of course, but even strummed rhythm parts can benefit from sounding more “blended together” (all strings displaying an even, sustained attack) and shimmery. Try a threshold of -6dB, a ratio of 3:1 or 4:1, a 150ms attack, and a 400ms release.
Bass. A great bass line should anchor a song, keep the groove percolating, and glue the ensemble together, so you don’t want the low end wavering dynamically, or not sounding rich and warm. Keep the bass levels even by opening with settings of a -4dB threshold, a ratio of 3:1, attack of 40ms, and a release of 180ms. Remember, as the dynamic range is reduced by compressing the bass, when you turn the bass level back up in the mix, you may notice muddiness, boominess, fret noises, and other less-than-stellar sounds you may not have noticed before adding compression. You may need to deploy EQ or other processing to get the signals sounding marvelous.
Drums. Unless you’re recording cafe jazz, drums should explode out of the playback speakers. You can use fairly aggressive compression settings to bring on the wallop, but the challenge is that reducing the dynamic gap between loud and soft drum sounds may bring a whole lot of signal bleed into the forefront of your drum tracks. Potential problems may arise from now having too much snare bleeding into the kick-mic track, hi-hats bleeding into the snare, overhead cymbals bleeding into everything, and so on. One trick is to send the kick, snare, hi-hat, toms, and overheads to a separate stereo bus on your mixer. Now, lightly compress or totally crush the stereo drum track—your choice or try both and everything in-between—and fade the compressed sounds back into the main mix along with the (uncompressed) individual drum tracks. Now, you have the organic drum tracks and a compressed stereo version to blend together—much like determining a wet/dry mix on a reverb—so it becomes a bit of a “have your cake and eat it too” scenario. Alternately, you can easily compress the individual drum tracks. Start each piece of the kit at a threshold of -4dB, a ratio of between 4:1 and 8:1, a 5ms to 15ms attack, and a 50ms to 200ms release. You may want to back off the overheads a tad, as every part of the drum set bleeds into those mics and compression will bring them all together into a percussion pie. Perhaps try a threshold of -2dB, a 2:1 ratio, a 20ms attack, and a 300ms or higher release.
Mastering. Successfully mastering audio requires big ears, a ton of experience, and a dollop or two of taste. You can find scores of articles online about common self-mastering mistakes, and I don’t think they are written by audio professionals looking for mastering gigs to scare home-studio musicians away from a DIY approach. Those pieces simply illustrate how hard it is to do mastering well, and why good tracking engineers are not always awesome mastering technicians. So, perhaps think twice about mastering your next CD, vinyl, or streaming project. But if you want to get a music production mastered for playback on YouTube, TikTok, Instagram, and other social networks, then start with light compression. You want the track to sound loud and proud on laptops, mobile devices, and earbuds, but you don’t want the music to appear dull, lifeless, or thick. Begin with a -2dB threshold and a 2:1 ratio. Rapid attacks tend to make a stereo track smooth and relatively natural, while slower attacks bring on punch and impact. Release times of 300ms and up can help prevent listeners from hearing the compression pump and breathe—something you very much don’t want in a stereo master track for public consumption.