Choosing a mixing engineer is a key part of producing a song. A good mix can help a good recording shine, while a mediocre mix might make it sound flat. Since it's not common practice or recommended to record or re-record parts after a song has been mixed (although in rare cases it happens), mixing is undeniably a milestone in the production process. It's a point of no return. As a result, it's where musicians and producers have to 'let go' and put their faith in a specialist to do their recording justice. Let's start from the top.
What is mixing?
Music mixing is the process of taking a multi-track recording and 'mixing' it down to one single stereo track (left and right). Before mixing you have a multi-track session – for example 12 individual drum tracks, 6 vocal tracks, a bass track, 2 guitar tracks, 4 keyboard tracks totaling a few dozen tracks. After mixing you would have one stereo file. This audio file is almost the final product for distribution. A song is truly 'done' once the mix is mastered. So why is mixing so important? Because of what happens during the mixing process. A mixing engineer does much more than just 'combine' the tracks. You see mixing is all about context, the way individual elements of the arrangement behave, sound and feel relative to each other, and how that affects the overall experience of the listener. The mixing process can be divided into the following main parts. An easy way to understand them is through the tools the mixer uses for each. The combination of these things the mixer does hugely affects the sound and feel of the recorded song, which is why good mixing is so important.
Balance and panning
One of the most important components of mixing is balancing the levels of the individual instruments relative to each other. Should the guitar be loud or soft? Which instrument takes center stage at which section in the song? Balancing the levels of the individually recorded instruments might sound easy, but it's an art form. It's also dynamic. The level (volume) of a track (such as an instrument or voice track) does not stay level throughout the song. Different instruments typically take center stage at different moments otherwise the song would be boring. And because most instruments are dynamic themselves, some leveling is necessary to ensure that they are heard even if they sound too soft or loud in certain parts relative to other instruments. Sometimes an engineer will also 'mute' (silence) specific instruments in different sections of the song, but typically this is done as part of the arrangement by an arranger or producer before the tracks are given to the mixing engineer.
Panning involves choosing where on the stereo spectrum tracks play. Since most music today is heard in stereo, individual instruments can be placed on the far left, smack in the middle, far-right, or somewhere in between. Panning is used creatively, to create a feeling of width and sometimes motion. It's also used surgically, to help the listener understand which instrument is taking 'center stage' (literally).
Equalizing and compression
After level and panning, two important tools in a mixer's toolbox (and on most mixing console channels) are equalization and compression. If you are not familiar with what equalization does, just think of the 'treble or bass' knobs on old stereos or the EQ tab in iTunes. EQ is used to manipulate (raise or lower) certain frequencies. Sometimes EQs are used to manipulate groups of instruments or even the whole mix. The frequency curve an instrument was recorded depends on how and where it was recorded and with what microphone (if it's a live instrument), and it doesn't necessarily sound the best it can, especially in context of all the other instruments around it. Engineers can make instruments brighter or darker, more bass heavy or thinner in very particular ways to make them sit better with other instruments and make sure they all have room in the mix. Equalization is used to treat instruments that fight each other for 'space' in the frequency spectrum, for example bass and kick drums, which share low frequencies that sometimes compete. They both may sound great on their own, but together sound muddy. EQing can be used to bring out the best of a track or hide problem frequencies in specific tracks. To make instruments poke out of the mix or to feel softer, to get more clarity or increase or decrease the perceived warmth or weight of a track.
Compression is used in two ways. The most common use for a compressor is to level individual tracks' dynamic range. Imagine a waveform that has big spikes and deep valleys and ironing it out, so the soft parts become bit louder and the loud parts become a bit softer. A good example is the human voice - a very dynamic instrument. Within sentences or even single words there are big volume changes. Since we listen to pop music on small speakers or ear buds, often in noisy environments, hearing all the nuances of dynamic instruments is difficult, especially if we hear them alongside a dozen other instruments. Compression helps. It enables the listener to understand every soft syllable of a singer's voice, while ensuring loud syllables don't poke out to be harsh. This is key for being able to enjoy a recording without having your hand on the volume knob, as well as for understanding all the lyrics even in the context of a busy mix and a noisy environment. Compressors are used to 'squish' and flatten out the roller coaster that is the internal volume of these tracks.
The second way compressors are used is as a creative affect. A really cool thing can happen when you exaggerate a compressor's effect and push it hard. It actually changes the feel of the instrument. It can make an instrument that sounded kind of wimpy feel strong or more urgent. It can literally make drums sound like they were hit harder than they actually were, or vocals sound like they have more urgency and pop than their original recording. Compressors can be also used to make certain instruments feel like they are 'pumping' if used in a certain way and to 'glue' certain instruments together if they feel disconnected. Compressors are magical sonic manipulation tools, and when used correctly, can add character. This is why engineers love them so much.
Creative effects – reverbs, delays and more
A mix engineer's arsenal includes other creative effects for making songs sound more interesting and add 'ear candy'. Reverbs, delays, distortion, filters, chorus, flangers are all popular creative effects. Reverbs and delays are probably the most popular of the bunch and are used to add space and depth to mixes. Adding reverb or delay to instruments makes them sound like they are in a physical space. Since most tracks these days are recorded with the microphone very close to the source, they end up sounding up very close and dry when played back. Reverbs and delays address this problem and psychoacoustically place that same dry recording in a lush space. There are different flavors of reverbs and some actually have names of spaces like 'small club' or 'large hall'. By adding reverb and delay tracks sound 'farther away', providing an awesome way to give the mix depth. Keeping certain instruments 'close' (dry) and others 'far' (wet), creates an illusion of space between them. Too much or the wrong type of reverb or delay will quickly make a mix sound cheesy or amateurish. When used well, they can be beautiful and moving. You can use short and minimal reverbs for an intimate sound, or big ones for a dreamy or stadium effect. Reverbs and delays are sometimes used to soften particular tracks that otherwise sound harsh and dry, and other times to glue instruments together and make them sound like they were recorded in the same room when they were not. Some popular uses for delay include slap delays (think Elvis or John Lennon vocals) or echo repeats synched to the song rhythm (as you can hear in many pop productions). These echoes can be made to sound washy or well defined.
Mixing is about skill, taste and knowing to serve the song. The same song can be mixed in many different ways. Mixing entails many creative decisions and skilled 'moves' and when done well it can truly make a song shine and be interesting.
Choosing the right Mixing Engineer
There are many mixing engineers out there with varying styles, experience, expertise and levels of customer service. Here are questions to ask and things to look for that will help you make a decision about whether a mixing engineer is the right partner for you.
There is nothing more helpful to understanding an engineer's style and skill than listening to previous songs they've mixed. A sound sample can speak a thousand words and you should trust your ears. One thing to keep in mind is the tracks they worked on might be different than yours in style or recording quality and that can make a big difference. It's fair to ask an engineer if you can expect similar results after you discuss price and send them a rough mix or your tracks. At that point, they should have enough information to tell you if you can expect your mix to be in the ballpark of the samples in their reel.
Every engineer has a different mixing style, and that's natural. This is no different than musicians who are more connected with and (have more experience in) a particular genre. A mixing engineer's style will often depend on what music they like, what they work on most often and their abilities. Really 'getting' the nuances of a any genre is key to nailing that sound. There are engineers who are eclectic and work on a wide range of genres, but finding a specialist is often helpful. I recommend listening to an engineer's reel to get an idea of what their style is. If an engineer really connects with your genre of music, that will make a huge difference. Mixing engineers are geeks and if for example they like EDM and work on a lot of EDM, they will already know how to get that pumping sound you might be looking for and won't have to start experimenting. The approach for EQing a kick drum or bass for a Jazz track is totally different than for a rock song. If you don't hear a track in your genre in the mixer's reel you can always ask if they have one that wasn't included.
This one is obvious. Mixing engineers work with a wide range of budgets, like everything else in life. Don't approach a Grammy-winning engineer if your budget is $400 per song (hint – the top ones charge thousands per song). In the same vein, don't expect your mix to sound just like Katy Perry's if you recorded the song in your bedroom and have $200 per song for your mixing engineer. There are young passionate engineers who will work all night for you for $200 and might get you a significantly better result than what you can get yourself. Be realistic about what you're willing to spend and what you're expecting in return. In general, rates start at $200/song and go up to several thousands per song. You start having access to very experienced engineers at around $500 per song. Tip - Some engineers will cut you a deal on the per-song rate if you pay for multiple songs in advance. Some of the things that determine an engineer's going rate are their years in the business, their credits (this is a big one), reviews, their skills, their gear, and their availability.
Some mix engineers want payment upfront, some half upfront and half on delivery. You can choose what you feel more comfortable with; just make sure you understand what payment term a proposal includes before you choose your engineer. If you really want to work with someone but you don't feel comfortable with their payment term, you can ask them to change it and they might agree. Be fair and sensitive to the engineer's time spent on your music.
Credits and Reviews
World-class engineers rely on their credits to speak for their ability. If you've heard songs they've mixed on the radio you know the level of skill you can expect from them.
For engineers with fewer or lesser-known credits, reviews are a powerful alternative. By reading what other clients have to say about working with them, you'll get an idea of whether they delivered on the clients' expectations. All musicians are emotionally attached to their music. If numerous musicians gave a mixing engineer a great review, you know that not only the engineer delivered on expectations, but they likely also gave good customer service. Finding an engineer that will take the time to realize your vision is important. An engineer might have skills, but if they aren't open to accommodating your feedback you run the risk of having an unpleasant experience or not getting a mix you are happy with.
The gear an engineer uses is less important than the other things above. There are awesome sounding radio mixes that were done all 'in the box' (i.e. mixed in the computer as opposed to on an analog mixing console). A great mixer can do wonders on a laptop and a mediocre or wrong mixer for the genre can butcher a song on an analog console. Don't believe the hype. Nonetheless, it's worth looking at where an engineer works and what gear they use. It's just one more factor in understanding how serious they are about their trade. Are they in an acoustically un-treated bedroom with a laptop and mediocre speakers, or are they going to mix your music on a professional console in an acoustically treated control room? Most engineers these days fall somewhere in between on that spectrum. I wouldn't make gear the deciding factor, but I do recommend taking note.
Working with a Mixing Engineer (or Help them help you)
Giving good directions
Since there's a creative element to mixing, it's important to be on the same page as your mixing engineer. When making creative decisions a mixing engineer will feed off of your production approach, rough mix, and notes. This doesn't mean your rough mix needs to be great, but it means it should give a general directive of the balance, panning, and style you're hearing. If you envision the piano being upfront, almost on par with the vocals for example, your rough mix is a good way to let the engineer know that. Another very helpful thing is including notes. Example of track-specific notes might be 'I'd like the kick to be huge and heavy' or 'I'd like the snare to drive the song and have a whap (or alternatively a 'thud'' or 'I'd like the vocals to be dirty, maybe even a bit distorted' or 'lets go with aggressive sound on the drums, like The Killers', 'I want the synth to be soft in the verses and loud in the C-part' or 'lets keep it very organic and dynamic' or 'the strings should feel in the background except for the ending' or 'I like a lot of delay or reverb on my vocals like U2', or 'The background vocal should be way lower than the main vocal'. Insider Lingo – Sonic adjectives used often are 'clarity', 'warmth', 'urgency', 'tight', 'wet' (which often translates to a lot of reverb), 'wide', 'dirty', 'clean'.
If you are asking for a particular instrument to be loud, remember that 'loudness' of an instrument in a mix is only relative to the level of other instruments. There's no such thing as an instrument being loud in a vacuum. After all, the end-listener has the overall volume knob. There is only 'louder than something else in the mix' tricking our mind to feel it as loud. So avoid asking for all the tracks to be loud. You (or the producer) need to choose 2-3 elements you want to feel 'louder' than others in the mix and convey that to the engineer. It's important to choose what takes center stage. If everyone takes center stage, no instrument gets the spotlight and you get a bad mix. You may want the overall mix to be 'loud' and you can let the mixing and mastering engineer know this. Keep in mind the price of overall loudness is dynamics (certain parts feeling louder than others). Older recordings like Pink Floyd's 'The Wall' for example are not loud overall, but are very dynamic – song climaxes are actually louder than the softer parts.
Many clients also include a reference track in the form of an mp3 or link to a youtube song. This is super helpful, especially if you find your directions get lost in translation. No need to figure out how to professionally describe that drum sound if you can just play the engineer something and say 'that!'. If you send an engineer a link and tell them 'this is the sound I'm going for', it can provide a helpful reference. It's very important in this case to be reasonable in your expectations. If your arrangement and production is very different than the one for the reference mix, it will be hard to take away what the similarities should be. Also, if the reference song you sent has a high quality production, with great instrumentation or samples, awesome performance recorded in a great space and your song was recorded in a weekend with less than stellar performers or gear, don't expect the mix to make-up for that. What you put it will very close to what you get out.
Preparing a song for a mix engineer
Preparing a song for a mixing engineer is well worth your time. If you don't do this work, they will have to do it, and wouldn't you rather they spend their time mixing rather than prepping or problem fixing? You want them to be inspired when they are mixing your music, not frustrated or tired from cleaning up or making sense of your session. Most engineers want clearly labeled 'stripes', which are consolidated audio files all starting at zero. They can import these stripes to whatever DAW they are working on and not have to worry about DAW compatibility, edits going out of sync, hidden files referenced in your session that take space but aren't being used, or having the same virtual instruments or plugins you used loading on their machine.
Getting your songs ready for mixing is actually quite easy.
First make sure you like your performance in all the tracks.
Fix any timing issues (very important), edit and pick the best parts for every track, cut and mute the parts that need muting to make room in the song and keep it dynamic (rather than everything playing all the time) and added fades to all edits and cuts.
Now carefully review every single track in solo and make sure the fades are clean and there are no clicks, pops or distortion. These are things that will make things very difficult for the engineer.
Next, create audio files from your virtual instrument tracks. In some DAWs you can do this with one 'freeze' or 'consolidate' command. If you don't have this option, you can buss each of your virtual instrument tracks to another audio track and record the whole pass. The goal is to give the engineer audio files that don't rely on them having a particular plugin or virtual instrument.
Make sure none of the tracks are peaking (hitting the red). If they are for any more than a split second once or twice, pull back their level.
Finally, export or bounce all your tracks individually as audio from session start (or all from exactly the same point) at the same file format, bit rate and sample rate as your session. For example if you recorded .wav files at 24/48, you should export all the tracks as .wav files 24/48. Mono tracks should be exported mono, stereo tracks as stereo. Makes sure all the tracks are clearly named and labeled. Depending on your DAW, track labels might carry through to the exported/bounced audio tracks.
That's all there is to it. Zip those babies up and send them to your mixing engineer.
As you can tell, mixing is part technical and part creative. Engineers spend part of their time problem fixing, and part of their time making a song more sonically interesting and fitting to the genre and intent of the producer.
Remember it's key to have a good song, good arrangement, good performance and good recording before getting your song mixed. Mixing is just one step in the process. It can help make a great recording shine, but it can't compensate if any of other foundations are missing.