Okay, so, it seems you need some external hardware if you want to use Pro Tools 8 LE.

What's it for, exactly, aside from processing your effects? Also, is there a cheap way to do this?

What I'm looking to do is basically just write music, w' Reason (in other words, make digital music, for production). I'm not using any external instruments or recordings.

(been Googling this for a while, but can't find many specifics about what exactly the hardware is for. I don't know any Pro Tools or music terminology, thus I'm just searching for stuff like "mbox", and skimming Wikipedia articles)

Pro Tools software has to work with Pro Tools "approved" hardware. As far as why? Partly because Pro Tools has a different set up and the more complicated the set ups (like with the HD modules) they have specialized chips that process the FX instead of your CPU which improves performance. The other reason, honestly, is because they want to be elite. Set apart. My MOTU audio interface can process DSP independent of the CPU or DAW just fine but it doesn't have the Pro Tools label.

Look up M Audio and Avid for different solutions. The most affordable would be the MBox Micro which is basically almost like a USB dongle. Then it goes up from there. But if you're wanting to use Reason then you really DON'T need to go the Pro Tools route. Especially if you're not looking to use Pro Tools software. You'd be much better getting a 3rd party audio interface that will work with a wide variety of audio software and not cost as (some) of the Pro Tools interfaces. I have a MOTU 896mk3 audio interface and it has been rock solid. But that's oddly more power (and cost) than you're looking for. Look at their full line. Since you're not needing any inputs (at least not right now) you could probably get one for roughly $200-$300. Maybe even less.

Thanks,

Nate

For music composition, ProTools isn't really worth the money I dont think. As long as you know and understand the DAW inside and out, a cheaper alternative such as Cubase or Sonar will achieve just as good results. Instead of spending so much money on an expensive interface, you could perhaps purchase some nice plug-in's/libraries?

One note to tag onto molecularsounds's post:

I would NOT suggest Sonar if you ever intend on doing any post production work with video media. Sonar is a very capable program in many regards but it totally SUCKS when working with video. Something like Cubase (or even Reaper) is much, much more functional. Sonar also doesn't handle it's RAM and VST plugins as effectively as other programs like Reaper.

If you're on a Mac - then go with Logic all of the way! Great bundled plugins, fantastic video support and rock solid AU (Mac's version of VST) support.