I want to be able to pull a specific frequency-band out of a track, like 400hz-1000hz, in order to manipulate it. I tried using [bp] and [line] but I can't get those to work. Of course it should be known that I'm very new to PD.

So, if you have extended you should check out all of the info that Miller Puckette has put together - mainly the audio examples where he will show you nifty ways of graphing the spectrum. You'll need this so that you can see how successful your efforts are. In my version you have to right click on the PD app and "show package contents" and it's under documentation 3) audio examples.

You won't need line unless you want to change the cutoff freq, and in that case you will want to use [vcf~] anyway (it's also a bp filter.)

Reading Puckette's chapter on filters has me pretty confused (real/imaginary anyone?) but the main thing that I took from it is that digital filters are bullshit compared to analog filters.

You couldn't get BP to work at all? What you will want to do is [bp~ 700 5] You may have better luck with [vcf~ 700 5].

It sounds as if you want a very steep curve at 400 Hz and 1000Hz. In analog circuitry a steeper cutoff would be achieved by basically stacking high pass filters [hip~] at 400Hz and stacking low pass filters [lop~] at 1000Hz. You can do the same in PD, though I'm not sure how well this will work. Again, digital filters are shit, which is why you need to study up on the spectrum graphing so that you can see just how bad they are. If I were you, I would get creative and just throw tons of the built in filters together (hip lop bp and vcf) until you get something that "sounds" like what you want. For spectrum testing you will want to feed your filter network with a [noise~] object.

What are you trying to do anyway? And if you are thinking "extract voices from a mix" you might want to study before you post a response.

Feel free to ask questions about how to make PD make sound and basic stuff, it's really a pain in the ass but really fun once you understand.

Thanks for the informative response, PonZo. You've given me a lot to try out and think about.

No, I don't want to "extract voices from a mix."

I was thinking more of having a sample being split up into different frequency bands (1-399, 400-1000, 1001-5000, etc.) They don't specifically have to be those ones, but you get the idea.

As I said--I am very new with PD and am still learning things. So although I used [bp], I probably wasn't knowledgeable enough to use it as creatively as you have described above.

I do have PD Extended, so I'll keep reading the documentation, which has been pretty easy to follow.

i guess the way ponzo mentioned with a stack of hi-pass and lo-pass should get it to work, but i think you should check out, if there are fir-filters you could use for that. the slew rate of iir-filters is not steep enough for isolating precise frequency bands.

For some reason I've found that stacking [hp~] results in a really loud output, so be careful if you go that route.

If you're feeling adventurous, you could take a look at the FFT stuff. Basically, you'd want to do an FFT analysis, split the bins into different groups, and IFFT each group separately.