There was a vid on youtube that showed you how to make one within Reason using a mixer.. Something like routing the sound thru various channels that have the frequency bands set to a different range.
Cant search myself now as at work but was posted here recently.
trueRTA is a free one. But there are loads. I cant remember the name of the one im currently using (at work)
You are best off getting a demo of one just to make sure it works with your sound card - as some of them dont work that well - before you pay out any dosh.
then you can see if its any good for what you want.
as russia-dj said you can "make" an analyser using stereo imagers - i can send u the combinator for that if u want it
You can do it in reason using the Vocoder Unit, its not very accurate though
I dont use one, i just have a look at the windows media player to get a rough idea, tbh use your ears matey, a badly mixed tune could look alright on the analyser