How to apply effects to only some frequencies?

Is there a sensible way to split up an audio stream into different frequencies, apply effects to only some of those frequencies and then mix them back together without completely messing things up? I approached this problem naively at first and quickly realised that it's trickier than I originally thought. What I'm ultimately trying to do is apply sidechain compression to only specific frequencies so I can bring out the thump and the slap of my bassdrum through what will be an unpredictable audio stream.

you can do some fun stuff with phase cancellation. track 1: put source material here. track 2: this is your eq splitter. track 3 is sourced from track 2 output. put your HF processing (or whatever) here. track 4 is source from track 1 minus track 2. put your LF processing (or whatever) here. to monitor, solo track 3 or 4. double check it doesn't do anything weird with phase though! seems okay here but.

Wow thanks for all the quick replies!! stupeT: reaXcomp doesn't have a sidechain as far as I've noticed otherwise I would have used it. zappadave: I'll have a look at the JS splitters and see how I get on. dub3000: I tried that and maybe I made a mistake in the way I set it up - I'm fairly new to reaper and to production - but the end result had "something" wrong with it. I'll have a look at how you did it and have a fiddle!

The old-school approach, and where multiband compression first came about, was to simply split off a signal to two or more mixer channels, and then use an eq to isolate certain frequency bands in each channel, process them however you want, and then sum them back together. This is so easy to reproduce in Reaper or any other DAW that I doubt specific instructions are even necessary. Actual multiband compressors and such make this task easier to manage. But REAPER actually includes some very sophisticated features that allow you to build your own multi-channel effects chains within a single track, greatly simplifying mixing and signal management. Nicholas' REAMIX guide is well worth the price of admission for his detailed and reaper-specific walkthroughs of these features alone. If you're a beginner to recording, REAMIX is a very valuable technical and aesthetic guide to general mixing. If you're experienced with conventional recording, it's actually even more impressive as it really gets into some of the incredibly powerful features that specific to reaper and that could easily be missed. Check it out.

Hi All, I understand reaper's routing capabilities, I was just wondering what the BEST way to go about it is ie. avoiding any loss of quality. Could someone confirm this ill effect for me: In the attached project there is one track which I have left empty as I used a commercial mp3 in it for my experiment - add a track of your own liking. In the other track is a 5 way splitter followed by a 5 way joiner. By soloing each in turn, you can hear the difference - the obvious difference is in volume but if you turn up the level of the splitter and joiner track, you can hear that they are not quite the same. Is it the splitting and joining that effects the outcome or might there be another reason that I hadn't thought of? Cheers