Here at the studio, we have mixed down quite a few tracks over the years. A lot of the time I see producers making the same mistakes over and over again in their own mixdowns. I'm going to let you in on a few secrets - some may be old to you, and some may be new, but they all are important in every mixdown! Let's start with the big one. . .
There's mud everywhere!
By far, the thing I wind up fixing in people's mixes the most is the low end. House producers realize that in their genre the kick and bass are essential elements, so they just make them loud, right? Wrong. Boosting bass is one of the last things want to do to have a full, lovely sounding low end in your mix. What should be done first is clearing mud, or creating space, by EQing everything else. Every single sound in your song has some low frequency information in it, whether you're using samples, VSTs, or recording live. A hi-hat, for example, obviously is a higher pitched sound mostly lying above 1kHz, but will still have noise all the way down to 10-80hz - where the bass and kick live. That quiet low frequency information adds up from all of your sounds, makes your mix muddy, and prevents the kick and bass from being heard clearly. Using high pass filters on EVERY sound in your mix EXCEPT FOR the kick and bass is often not a bad idea. Seriously. I do it in my own productions all the time.
To do it, just listen to the instrument you are currently EQing in the context of the mix, start your high pass filter down around 60hz, and sweep up the spectrum slowly until you hit the frequency that you start to miss something in the sound. Then, bring the filter back down a just a little bit. You will be surprised at how much you can cut off the bottom of all your sounds! Clear away below 80hz-250hz on every other sound and your kick and bass will suddenly sound like a sheet was lifted off the speakers. Clarity, not mud!
2. Snap, Crackle, & Pops
Have you ever placed a sample onto an audio track, looped it, and heard strange high frequency pops each time the sample triggers? If you haven't start listening! The phenomenon of 'bad enveloping' will lead to pops and snaps in your audio that will be brought out later in mastering and may wind up being quite distracting. Take a long kick drum sample and paste it into your DAW. Use a kick sample that is longer than a quarter note. Then, duplicate the kick every quarter note to repeat on each beat so that one kick is still playing when the next kick hits. If the first kick drum doesn't come back down to -inf dB before the next kick drum hits, you will often get a popping 'snap' sound on the attack of the next kick. This is because your DAW is trying to read the signal as a smooth waveform, but repeating samples without proper enveloping results in unnatural jumps or skips around the waveform. A lot of drum samples being sold today also have a bad pop at the end of their samples. This is because they didn't take care when making their samples and didn't gate/fade off the sound back to -inf before the sample ends. Try using gates, envelopes, or volume automation to bring your samples and loops to silence between hits. Adding a very fast attack and/or release envelope of your sound can sometimes eliminate this problem, as opposed to just triggering the sample to play its full volume start to finish.. Be aware that sidechaining without proper lookahead or attack and release settings will create high pitched popping artifacts too. I hear these popping artifacts in finished, commercially released music all the time, and it drives me nuts!
3. Make Sound Choices
The way your final track will sound is influenced by every single step in the production process. There is no way a mastering or mixing engineer can take a poorly constructed track and turn it into something that sounds like a million dollars. A lot of those killer tracks you wish you could sound like are being made with high end gear - not poorly recorded samples or cold sounding VSTs. Mixing or mastering cannot make poorly recorded sounds seem high end. Try to get everything sounding good AS EARLY in your production as possible, ideally while you are still recording. You'll hear studio engineers say to 'get it good on the way in'. Quality initial sounds translates into super quality mixes and masters. Poorly recorded samples or sounds that fight each other for space will ruin your chances of getting a great mix before you even get too far.
An often undervalued part of getting a great mix is selecting sounds and instruments that work together right from the gate. Songs are like movies - they can only have so many star players in them. You need a lot more extras than celebs! Think about which sounds do you want to dominate your mix, and make sure they don't fight. For example, if you intend to have a massive bass heavy kick AND a massive bassline, you're going to need some advanced wizardry to make it work - that's for another day. When you're picking which sounds to use in your track, make sure you're picking things that sound as close to what you'd like your finished product to sound like. Put good in and get better out.
EVERY single step in recording is crucial in getting 'that sound' the professionals have. You must be thinking about your mixdown early on and throughout the recording and writing process, making sure the sounds you select work together and have space. You must clear mud and pay careful attention to even small artifacts brought about by poor enveloping or digital effects. What you can't do is expect magic to happen at the mixing and mastering stage - engineers CAN make things that already sound good sound great, but can only make things that sound bad sound a little bit better.