I want to make a filter with an arbitrary amplitude response.  

I think I could do this with the convolve opcode, but it requires an impulse response, and I don't know how to derive one from my desired amplitude response.  I suppose I could use Csound to create a file of floats representing the amplitude response I want from 0 to the Nyquist frequency, then somehow edit that into a .cv file, as if cvanal had made it, but I don't know the format of .cv files and I've never edited a binary file directly before.

Is there an easier way to do what I want, and, if not, how do I prepare the .cv file?