DAW Fundamentals — Mixing Audio
What is Mixing?
Mixing takes on many forms and difficulty levels, based on how well the tracking session(s) went and what kind of music it is. A great, acoustic session might mix itself if the musicians are good enough, the mics are placed well, and the room sounds great. For a pro record, a mixer is usually given way more material than is actually needed, and all of it needs some work. The basic goals of mixing are:
• Mix volume levels within and between tracks so all audio is the ideal volume at every moment.
• Place every sound in the stereo field to add interest and keep things from
• EQ audio so that each band is appropriately represented and each track sounds its best in the context of the song.
• Audio cleanup and pitch correction.
• Apply effects (explained on the next page). Automate effects parameters (explained after effects).
• Mastering (explained at the end of the next page)—usually presented as the stage after mixing, not part of the mixing process itself.
Comping: This is the process where the mixer takes many passes of audio and creates a single, cohesive track. Some recording sessions use endless punch ins until a single track is perfect, some get a perfect take after a couple tries, and others are track after track of stored passes. It’s not uncommon to have dozens of tracks of the same material, and if it’s from sessions on different days, you could really be in trouble. One thing Bobby Owsinski urges is to not postpone making the hard decisions. If a take wasn’t great, delete it during tracking; then you don’t have to worry about it when it comes time to mix. Comping employs the split and crossfade tools often.
Mixing Levels: This is what most people think of when they hear “mixing.” You get in front of a mixer and you slide faders up and down until everything just gels. In a DAW, it usually gets more complicated than that. A beginning mixing engineer may just get every track up to the same volume and call it good. A great engineer will bring keep the dynamics of the song as interesting as possible. If the song doesn’t breathe like a living being and
The arrangement itself plays a huge role in how things interact in the mix. A great engineer can’t make up for a terrible arrangement, but a great arrangement can become breathtaking with the right mix. Good arrangements already have instruments that sound good together; if two instruments would conflict, the arrangement already has them sounding at different times. or in a way that will sound good anyway.
A good mix has a great foundation, usually bass and drums; harmonic layers, like synth pads, strings, or keys; instruments for rhythmic interest, like shakers and guitars, really anything that plays against the main beat; fills, for interest; and the leads—vocals and solos. The engineer considers all these elements and which ones should be more present at any given time.
Panning and the Stereo Field: Almost every mix is done in stereo. A left and a right speaker each sound, creating three main aural points of interest—left, right, and center. This gives the engineer a wide canvas to place instruments. It allows competing instruments to get out of each other’s way, and for the most important elements to stay far enough away from everything else.
• Generally, leads are placed dead center; the lowest of frequencies are omnidirectional and don’t compete with leads, so they are in the center as well.
• Things that were recorded in stereo are usually fed to both speakers, to maintain that same separation between left and right.
• Mono tracks are placed where appropriate. Often, mono tracks are doubled, delayed by about 20ms, then placed far right and far left. This creates the illusion that the same sound is coming from both sides. Another way to place instruments is to reproduce where they are on a live stage. There are some tools that do this with scientific precision, like VSL’s MIR Pro (more on that in the section on reverb).
Closely related to the stereo field is mono compatibility—it’s in the back of every mixing engineer’s mind. At some point, a mix will be played in mono. A lot of large-format systems (most places with in-ceiling speakers, in-the-round seating, stadiums, cafeterias, etc . . .) only output audio in mono. If anything between the right and left channels is out of phase when combined, then you’ll hear those frequency cancellations in those systems. Again, proper mic placement solves much of this issue, as does a good arrangement. The best way to achieve mono-compatibility is to mix in mono at least part of the time, even when panning; when panning around in mono, you’ll hear where the instrument is the most present and unaltered. Flipping phases of tracks while in mono is helpful as well.
The most accessible resource on learning about the stereo field is The Art of Mixing, as seen in the resources section. It visually teaches great placements for many styles of music. The author also observes that the stereo field isn’t just an X-axis phenomenon, it also has depth (via volume/presence).
Equalization: Most EQs uses phase cancellation/reinforcement to boost or cut different frequencies of audio. This can have a huge impact on how good a track sounds. I’ll go over EQing individual tracks in depth on the effects page. For mixing, EQ can help avoid clashes between instruments. For example, if a lead vocal sounds best from 2-5k, then that same band could be lowered in other instruments with a similar frequency range; this makes the vocal pop out in the mix a little better. When making these kinds of decisions, try to consider the effect on the entire mix, and not with the track playing back alone. A rookie mistake is to have every track sound amazing on its own, without regard to how they sound together.
Audio Cleanup: Basic cleanup involves dipping the gain when breaths are too loud; EQing out the band where a noise exists, so it isn’t as present; cutting and fading judiciously; etc . . .
Tools like iZotope RX 6 are mathematical wizardry (and 50% off for students/teachers). Their algorithms can clean up audio issues that are completely unrecoverable with just a DAW. This is where you can sometimes repair audio that has gotten loud enough to distort (a process called de-clipping, which attempts to redraw the waveform that was never recorded). Noise can sometimes be significantly reduced. Pops, clicks, breaths, passing birds, hums, and other sounds may be gotten rid of or at least reduced. With advanced tools, you can match EQ and reverb with other audio tracks, among other things.
Pitch Correction: These tools get real criticism at times, but are a wonderful time saver and a great creative effect. The classic auto-tuned effect was pioneered by Antares, and they still make great plug-ins and hardware units. Waves also
Melodyne is the premiere plug-in for sounding natural. It has several versions, and the most expensive one can fix wrong notes within the chords of some instruments (mostly for piano and guitar).
Resources for this Section
After nearly 200 pages of well-explained mixing principles and steps, there are another 100 pages of interviews of star mixing engineers to glean from.
David Gibson offers a uniquely visual guide to mixing. It’s a highly accessible and comprehensive guide.
This site hosts a very large library of tracks for mix practice. They include pretty much any genre/fusion you can think of.