Arrangement has definitely a lot to do with it. I used to wonder why some of my emerging music would just sound pin sharp, clear and separated right off the bat without any EQ at all, whilst others would quickly descend into an unholy slop with everything stepping on each other. Then it dawned on me that the big difference was arrangement and sound choice. Arrangement: everything sitting in its own little range of pitch, not too much in any area. Where there are pitch clashes, those parts interweave around each other so that they aren't playing notes at the same time.  Sound choice: everything occupying its own little slice of the frequency spectrum.
 
Of course all of this is easier to deal with when you're working with synths and MIDI since it's a lot easier to transpose parts, re-figure chords with inversions and tweak frequencies at the sound source before you even get into EQ. Plus there are a lot more "kinds" of sounds you can use than if you're mixing a straight ahead rock track.  

Besides using my ears, I have found it useful to use MMultiAnalyzer. It is simple and I like to see multi tracks freq spectrum on one screen to see how they compare. This can help me better identify an issue I am trying to chase down.

Danny Danzi
It's actually simple to handle this one beeps. :) When you boost a particular frequency, you cut that same frequency in another instrument and boost something else if need be. For example, most bass guitar today is lower in the eq scheme of things. You may get bass as low as 50 Hz at time. So if that's where your bass is going to be, you make sure and cut 50 Hz in your kick drum. This way it keeps it out of the way of the bass...which is where most of the masking comes from, low-end wise.
 
Guitars tend to get lost with other mid range instruments. Keys and even vocals can even fall into this category depending on how they are delivered. To try and prepare for this stuff ahead of time, it's been good for me to choose whether I will have a clicky kick drum or a bassy, thumpy kick drum. Whatever I choose dictates what my bass guitar will do.
 
For example, let's say I want to push my kick drum in the low end area at about 61 Hz. I will let my bass probbaly hit in the 75-90 range Knowing me in that particular situation, bass would probably end up at 80 Hz with a little bass clack at about 2.5k. Kick pushing 60-70....a little beater attack and maybe 8k....mess with mids and low mids to taste if needed.
 
The key to handling masking is to high pass correctly and at the right places and never boost the same freqs on different instruments. This is where the masking comes from. Like, you may have a sweet spot for 55 Hz because it gives you a nice amout of bass. If you push both the kick drum and the bass guitar there, you'll be turning up the bass fader and then the kick fader and then the bass.....because they cancel each other out.
 
Same with mid range instruments. If you boost say 860 Hz on a guitar to make it a little warmer, you have to be careful with piano, strings or vocals that you may want to warm up. They will cancel each other right out. Panning and proper compression are essential too as this will help to keep things out of each others way as well.
 
The two biggest things that cause this are:
 
1. Bad listening environment. Remember, you can never make the right calls if you aren't in the right environment. If you do anything with your money....do not buy gear, plugins or software. Get some good monitors and tune the room. This is so important, nothing else matters. Give me my tuned room, my monitors, Sonar, a guitar and a laptop running a Realtek soundcard with ASIO4ALL drivers and I'll give you a killer product. It's all in what you hear as well as making the right decisions based on hearing the right stuff. I can't stress how important this is.
 
Until you can get this, you're almost always going to fall either way short or short enough to bother you. I know funds are an issue as well as living space. But, you may just have to chalk it up and deal with what you have. It's rare anyone puts out great mixes through headphones....no matter how good or how pricey they are. No one in the big leagues does it....there's a good reason. Yes you can get decent results with cans, but don't stress out when you fail. It's not totally your fault.
 
2. Not sure whether to boost the frequency or just boost the level: This is another huge one. 9 times out of 10, if you just turn the fader of the instrument up instead of boosting the frequency, you just may be ok. A lot of times, people don't know whether to boost the freq, or turn up the fader. Always try turning up the fader first and try to be a cutter, not a booster.
 
When you feel you need more low end, try cutting highs and see how it sounds. If you need more highs, try lowering the lows. This isn't always the case so it won't always work, but you are better off removing mud and highs than adding them in. Ever hear a mix from the 80's? They were knida super thin and wide open for anyone to master on their stereo while listening. To me, that's actually an acceptable kind of mix because it's not loaded with low end like just about every mix I hear today. People are just over doing things so much, they are ruining their material. The more stupid plugins that come out that supposedly do all this crap or do things for you automatically, the worse people's mixes become. I've never heard so much crap in my life.
 
At any rate, don't stress out man. You can only go so far in headphones. I really feel there is only so far you can go. The reason being, you will have to compensate and try to "learn your cans". That's not how it's supposed to work. There isn't supposed to be second guessing or "my headphones naturally put out more bass, so I have to back it down in Sonar automatically". Stuff like that will knock you out every time. When I listen to something here, it is easy to fix because I can hear it. Everyone else that listens here says the same thing. In turn, wherever I listen to stuff, it sounds the same. There is never any second guessing or having to learn or compensate. When you can put that stuff behind you, the clouds open up and leave....and you laugh because this whole field just got 1000 times easier for you.....simply because you can hear correctly. :)
 
Hang in there dude, we'll do that video we talked about soon.
 
-Danny

Good advice Danny, Particularly with using fader adjustment first, Sometimes just a slight move of a fader may negate any eq adjustments.

sharke
Arrangement has definitely a lot to do with it. I used to wonder why some of my emerging music would just sound pin sharp, clear and separated right off the bat without any EQ at all, whilst others would quickly descend into an unholy slop with everything stepping on each other. Then it dawned on me that the big difference was arrangement and sound choice. Arrangement: everything sitting in its own little range of pitch, not too much in any area. Where there are pitch clashes, those parts interweave around each other so that they aren't playing notes at the same time.  Sound choice: everything occupying its own little slice of the frequency spectrum.
 
Of course all of this is easier to deal with when you're working with synths and MIDI since it's a lot easier to transpose parts, re-figure chords with inversions and tweak frequencies at the sound source before you even get into EQ. Plus there are a lot more "kinds" of sounds you can use than if you're mixing a straight ahead rock track.  

You know sharke, I have to admit I have never had this problem? I've mixed songs that had so many instruments, it was crazy. I didn't agree with some of the arrangements but they were never the reason why a song sounded masked or jumbled. The biggest issue I've had with complex arrangements or loads of instruments (try mixing something like Trans Siberian Orchestra...lol....I got handed one of their work files to mess with....yikes!!) is controlling like-frequencies and making sure things were panned.
 
The other side of the coin is something me and guys like bats have been preaching for years....the right instrumentation BEFORE a person tries to process anything. With most having very limited resources or not much money to buy a few things that could make a difference for the better, some sounds will just really make the recording field a nightmare for some. That was my biggest problem when I was learning this stuff. It's usually bass tones and guitar tones being the biggest offenders. With the drum modules we have today and synth modules, we're in much better shape than I was years ago using an old hardware synth that sounded fake. LOL!!
 
But getting back, I'm not disputing an arrangement being able to cause a problem. I'm just saying I've never encountered that. The sounds being horrible were more the culprit than the arrangement.
 
-Danny

As always amazing stuff for me to ponder and try out. Sorry I haven't been participating (doing some writing/tracking) but I've been watching intently.
 
Thanks!

just get this:
 
http://www.meldaproductio....php?id=MMultiAnalyzer