This is actually primarily intended for @Diego
to help him with his recordings, but I thought it might be worth posting a more generalized overview of the topic in case it helps anyone else. Obviously most of us are primarily singers so we want to show off our voices, get feedback and critique and generally do what singers do and perform. We all post clips or full songs, whether it's on YouTube or wherever, and record on everything from our phones to fancy shmancy set-ups with good quality microphones, etc, but regardless of the source there are simple ways to make your recording sound better (or worse if you mess it up!). They're so simple in fact that we will, with absolute certainty, screw them up repeatedly until we get it through our skulls that, just like singing, there are easier ways to go about it and get effects that sound great. I'd like to address the topic of doing some basic equalisation on your vocal tracks and offer some stuff I've learned so far that might save you some time, and improve the clarity of your demos.Example Vocal Waveform
In the image here, I've used a dry vocal from a cover I'm working on of Crash Test Dummies "Mmmm Mmmm Mmmm Mmmm" which is sung away down in the first and second octaves. Due to this and the natural tonality of my voice at that range, there's a LOT of activity in the low-end and in the lower-mids - Look at how the wave looks much higher from about 70Hz to around 300Hz with only a slight dip. Because I'm a baritone, my voice resonates down to 50Hz and can go into sub-bass territory but it's absolutely, completely and totally useless to anyone! This is why, if you look at the very, very rough EQ curve below the main image you can see I've started to cut off everything below around 100Hz.
"Doesn't that mess with the sound? Don't you lose that Barry White vibration?!", I hear you say...kinda...but it's a good thing because those frequencies will create a sonic swamp once you start adding in other instruments in that range, such as guitars, drums and bass. If we remove as much of the lower end from the vocal as we can without losing the richness and resonance, we create a massive space for other instruments to fit in later. Look at my example. Now I know immediately that I can sit a bass and a kick drum in there comfortably; the bass typically has a sweet spot in most commercial recordings around 68-72Hz, while your kick has weight and body down around 50-100Hz so you're giving yourself room to move later too. It also takes out any ground rumble or mic stand noise, which can mess with stuff later down the line in the mix so this saves you a lot of hassle with just a simple low-cut.
Due to that big peak around 140Hz, I've also taken out a wee bit of the gain around that area to remove some unnatural sounding lower-mids. As you can see, there are other very small cuts and boosts along the frequencies until we hit around 1kHz. Around there is generally where most people's voices have the power or at least where their power starts to increase as it's belting territory in terms of the notes associated with it. As I was singing fairly gently and with more focus on the lower range, there isn't a lot happening between about 1-5kHz so I've boosted things a bit to balance the sound a bit. I've also cut slightly around 1kHz as there's a tendency around that area for a certain 'boxy' sound to occur on vocals; a slight reduction can really open up the higher mids and high end.
Between about 5-12kHz is where the brightness is placed with a vocal this low, so that sorta sparkles on its own and only really needs a slight boost. You'll see that the boosted line continues until there's no more frequency showing. From around 8-18kHz is where we find what's usually known as "air" or the nice bright, shiny high end of a sound, so vocal recordings will usually benefit from a high-shelf boost around there. A problem here though is that this area is also where a lot of your hiss and noise comes in, and it's possible to accidentally EQ it and make it worse. You can also make vocals too harsh by boosting up here without really listening to your track. It's better to deal with noise problems using specific software or hardware as trying to EQ it out is both painstaking and frustrating, and ultimately not worth it 'cause you end up losing a lot of the top end.
Your vocal, in most cases, will likely sit largely in that mid to upper-mid range, so from about 1kHz upwards although those with higher ranges may find theirs has more activity from around 2-4kHz and above. An easy way to think about the main frequency range within which a human voice sits is to think of your phone. Since they were invented, they've only ever focused the sound within a very narrow bandwidth that peaks around 4kHz, although as technology advances this width is increasing to be more like real-life. Even then though, take something like Skype for example: You still lose of a lot of the bass and high-end, unless you run your input through some sort of interface to create a better sound. This is all because of that natural area of the spectrum where the human voice typically resides, and we can use this to our advantage by understanding how to exploit it, emphasise those golden overtones and bring out the sparkle from a seemingly drab vocal. It's all possible with nothing more than EQ.
Think of the ubiquitous "telephone effect" on vocals. This is easy to replicate using what's called a "bandpass filter", in other words an EQ curve that cuts off all frequencies on either side, leaving only a specific bandwidth audible. Slap an EQ on, cut off everything below 1kHz and then everything above 6kHz, boost it a wee bit around 2kHz or to suit the sound you want and, voila, sounds like you're on a phone. It needs refinement with a bit of overdrive and compression to really cut through a mix, but that's how you get the basic sound anyway and shows how easy seemingly complicated effects can actually be.
If you look at the picture and look closely after the 20,000Hz line at the right, you'll see a peak that seems to just sit itself, apart from the rest of the signal. This, my friends, is a cheeky wee slice of noise that's sneaked in on the recording because I have really crap mic leads! On a vocal this low, I could probably get away with cutting off everything about around 18kHz and then add that air back in later with compression and some further EQ. Normally though, if you can get rid of or avoid noise like this, you'll save yourself a LOT of time and hassle. Just remember though, you can always go back and redo it later if you find you've recorded noise in error. It's not the end of the world, much as it might feel like it in that moment...
I hope this is helpful and makes some sort of sense, but feel free to ask whatever and I'll reply whenever I can. As I'd said in another thread, singing and YouTube are literally my job so working on helping people here is all part of practice for me!
P.S. Tried to post this earlier but I think there were some problems site-wise, so my apologies if this double-posts.