Basically, I'm looking for a VST plugin (preferably FREE) that compresses the frequency range of a track. Unlike a EQ which cuts or boots specific frequencies, I want an effect that can compress the frequency range while keeping the original sound as much as possible (e.g. turning it from 40hz-20khz to 100hz-15khz)
Does such an effect even exist? I don't know why, but I can't find any...
That's still an EQ, you just cut the bands to -infinity. More specifically, you would want to use a shelf EQ if you have it. Also sometimes called high pass and low pass filters.
There is a Waves Multiband compressor plug-in which supposed to do what you're asking for. But it is definitely not free.
I can think of another way to obtain such effect, however it depends on which software you are using. I believe that in Cubase you can process a track with EQ and stream the resulting audio to a different channel (not necessarily in this order), then you can just compress whatever you get on that channel.
If you're using Fl studio you can use Maximus, This is a very simple and good plugin. It comes with Fl studio so it's kinda free.
If you're using cubase you can use the standard multiband compressor.
Melda productions has a free bundle with a lot of handy plugins for mixdown and mastering. You can have a look at that.
http://www.meldaproduction.com/plugins/product.php?id=MFreeEffectsBundle
Image Line has a multiband compressor VST - Maximus. Cakewalk has one in their Sonitus suite. Both of these cost.
Melda productions has one in their free effects bundle.
I agree with the others, you are looking for the combination of a multiband compressor and filters. Fortunately both of them are free if you have Reaper. It has a multiband compressor (ReaXComp) and an EQ as well (ReaEQ). And many more useful stuff. And Reaper is really cheap.
Dynamic equalizer.
E.g. this one
Such a tool probably doesn't exist because of some insurmountable physics problems. Sounds that have perceivable pitches are almost always made up of multiple sound waves. For example, if the note you're playing is an A at 440 hz, there will also be sound waves with these frequencies playing:
... and so on, oftentimes indefinitely (although higher pitches generally get quieter, until they are impossible to hear). The pitches above 440 hz are called overtones. Different instrument sounds are created by changing how loud different overtones are and whether they're perfectly in tune. (Effects processors that don't overtly change overtones always do so as a side-effect.) http://en.m.wikipedia.org/wiki/Overtones
The problem with a frequency compressor is that it would through off these proportions. As a result, the instrument world likely sound like it no longer was playing pitches! In extreme cases, it would have a sound similar to an untuned percussion instrument.
For example, if you compressed a sound that started at A 440 hz and had noticeable overtones up to 2200 hz, then compress it to 1000 - 1200 hz, the overtone pattern would change to
These pitches are too close together to create a sense of pitch.
