Resources for the Recording Musician
October 3, 2009

Fitting frequencies together

This is my first post on this forum. Somehow I lost my original post after I previewed it.

I read the article "3D and the Art of Mixing," I think it was called, where it discussed fitting frequencies together to keep mixes from getting messy, heavy, conflicting, etc....

My question: if two instruments both have characteritics of presence at 100 Hz, for the sake of the example a bass guitar and kick drum, and let's say they both come in at -6dbs, if I wanted the bass guitar to be prominent in the mix, could I EQ the kick drum and lower/drop the 100 Hz down to -7dbs solving the clashes of the two instruments at that level?

Would the bass guitar be the winner simply because it is louder at that frequency or would the two frequencies join together to form some amorphous beast?

Also, an instrument, such as a bass guitar, in an EQ analysis of its signal, demonstrates frequencies at 60, 100, 250, 1 K and so forth...if I am trying to "carve out a space" for an instrument frequency wise, cutting frequencies other than the the "fundamental frequency" leaves the instrument sounding dead or freakish. How do you know which frequencies to cut?

Again, if one instrument is "EQ'd" to get rid of some of its sound, when it appears by itself in the mix for a moment, won't it sound odd?

Thank you for your time and help.

I could easily write a book on EQ and mixing techniques, but there are several other great books already out there, and it mostly just comes down to practice, practice, practice, and then practice a lot more!

There are no super secret techniques, and there is no right way or wrong way to do anything in this biz.  You just keep practicing and working with it, developing your ears along the way and figuring out what works and what doesn't.  You pick up some helpful hints from others along the way that may work for you sometimes, and may not work other times.

Having said that, I'll try to give you some additional general guidelines to help you along, while trying not to write a whole book at the same time.

The lower frequencies of the spectrum are probably the most challenging to get "right" in a mix, so it's good that you mention those as an example.

In "most cases", you usually won't have the bass guitar and kick drum both trying to occupy the deep low end of the frequency range at the same time (100hz and below, particularly the 60 to 80 hz range).  Usually you pick one of those to have the deep bass, and the other for the range a little bit higher up.  A lot of times you really want the kick drum to have the low end thump (the 60 to 80 Hz range) and the bass guitar to be more dominant in the 100Hz and higher part of the low frequency range.  So, you'll shave off some, or maybe all, of those really deep frequencies from the bass, and perhaps beef up that range on the kick drum as needed.  Or, if it's more of an RnB or Electronic song with some deep sub bass synth type sound, you may want the bass to have the deep low end, and the kick to be a little higher up, so you remove some or all of those sub frequencies from the kick drum.

However, it's not an all or nothing thing.  It's just a matter of tweaking those ranges until the two instruments can sit well together without totally muddying up the low end.  Plus, to free up the low end for kick and bass, you'll usually remove most or all of those frequencies from all other instruments.

There are many other considerations, though.  Sometimes the bass and kick may not even be competing with each other if the arrangement doesn't have them playing exactly together.  In that case, there could be deep low end from both of them.  But, that's usually not the case, as the bass and kick are usually fairly locked together in most musical styles, so you simply have to make room for them to both work together one way or another.  Apart from frequencies, the tonal quality of the instruments can also affect how they fit together, as well as simply adjusting the volume levels until they fit together properly, or running them both through a compressor to keep the combined low end under control.

Another method of making the bass and kick work together, particularly if they aren't always playing right on top of each other, is to use a compressor with a side-chain on one of the instruments, triggered by the other instrument.  For instance, if the bass player is playing a lot more notes than the kick drum pattern, you may want to set it up so that the level of the bass is reduced a bit whenever the kick drum hits, so that the low end of the mix isn't overwhelmed when they both hit notes at the same time.  To do this, you would put a compressor on the bass channel, but set it up to be triggered by the side-chain input which would get it's input from the kick drum, so that the compressor is not working based on the level of the bass, but the level of the kick drum track.  Then, whenever the kick drum hits, the compressor would kick in and would lower the level of the bass by an amount proportional to the level of the kick drum (and depending on how you set the controls on the compressor).  This is harder to do with software systems since there aren't a lot of DAW systems that support side-chaining yet, and not a lot of plug-in compressors that have side-chain inputs.  Relatively easy to do in the analog hardware world though, as long as you own a hardware compressor with a side-chain input.

One thing you always have to keep in mind is the mix as a whole.  It's not really a great idea to solo and track and try to make it sound great by itself through the use of EQ, as it will never sound the same once placed in a mix, particularly if it's a dense mix (like a pop/rock mix with lots of distorted guitars and other instruments).

Bass guitar is particularly tricky this way.  If you solo up a bass guitar and make it sound really big, full, and deep all by itself, and then place it in a dense mix with lots of guitars and other instruments, all of a sudden your bass will sound very muddy and undefined.  On the other side, if you work with the EQ on the bass to get it sounding well defined and big in the context of the dense mix first, and then solo the bass track, the bass will usually sound fairly thin and wimpy on its own.

This is a trick of how we perceive frequencies, and is also the principal behind a lot of those bass maximizer type plug-ins.  You can actually totally remove the fundamental frequency of an instrument, like the bass guitar, and leave just the harmonics, and your mind will fill-in those missing frequencies.  That's what bass maximizers do... they generate more harmonics, raising the perceived level of the bass without actually increasing the low frequency content (depending on how you set them up).  Using that, you can give the illusion of deep bass even on relatively small speakers that can't even reproduce deep sub bass.  So, many times in a mix, you don't need those really low frequencies in the bass guitar, and can let the kick drum have those.  In many heavy rock songs, if you were able to solo the bass, you would hear mostly the upper harmonics and mid-range of the bass (with a lot of attack and presence as well) that really allow the bass to cut through the wall of distorted guitars and sound big and full without making the low end all muddy sounding, and also allowing the kick drum to give you that chest-pounding thump in the 60-80 Hz range (the kick usually also has a lot of high frequency clicky attack added as well so it can also cut through and be heard on speakers that can't reproduce that low end thump).

Now, as you mention, if you set up your bass EQ as described above, but then all of a sudden there is a section where the bass is exposed (all the guitars drop out or there is a bass solo), then you would certainly have to set up a different EQ for that section of the song to fill back in some of those low frequencies you got rid of, and probably back off on a lot of the mid-range you added.  That's part of mixing... EQ doesn't have to be a static setting throughout the song, it can certainly change for different sections of a song as needed.

The second most critical region of the mix is the mid-range, where our ears are most sensitive, and where there probably is the most conflict between instruments.

The best way to clear up the mid-range and allow everything to be heard, is to start with a good musical arrangement!!  A good arrangement doesn't have similar instruments playing similar parts in the same frequency range at the same time, unless they are meant to blend together instead of being heard separately.  But, often as a mixing engineer you are presented with the challenge of a far less than ideal musical arrangement, and the band or artist is not open to letting you remove instruments from sections to make more room in the mix.  Given that situation, you have to work with volume levels, panning, and EQ, to utilize that entire three dimensional space to make room for all the instruments that need to be heard separately to be heard.  Thankfully, since our ears are most sensitive in the mid-range, we can pick things out easier in that range than we can in the super low end, so we usually don't have to carve out such big holes in the mid-range to make things work together.  But, there could still be plenty of work to do depending on how many tracks are playing at once in a specific frequency range.  Many times it's just a matter of figuring out what is the most critical instrument or part in each part of the song (usually the vocal), making sure it can be heard clearly and sounds great in the context of the mix, and fit everything else around it the best you can.  Bring the volume down on the other instruments that aren't critical, carve out some frequencies in the non-critical instruments that are getting in the way of the critical ones, pan things left and right, and totally mute the least important parts out of sections of the song if the artist will allow it and it doesn't make a significant difference in the overall impact of the section.

Hope that helps clear things up a bit.  Again, practice, practice, practice, and then practice a lot more!!!  The more you mix, the better you will get!

Thank you for taking the time to respond so in-depth to my question. Excellent information. Could you suggest some "required reading" on the subject?

It's on my Required Reading list on this site, but worth listing here again.

The Mixing Engineer's Handbook - by Bobby Owsinski

Great book on mixing, and definitely a must read if you want to improve your mixing skills!

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