Hi Andy,

If you know the fundamental frequency, sure. But if you have to start by assuming the fundamental frequency, then you just increase the uncertainty of your measurement. Doing an FFT is just too dead easy not to do it.

Now where your point will apply is with regard to the Nyquist frequency. Since all of the harmonics from above the Nyquist will alias back into the measured spectrum, and since he doesn't care what their actual frequencies are, there's no need for heroics when choosing a sampling rate. As long as it's known to be sufficiently above the fundamental frequency for a good measurment, whatever rate is easy and convenient will suffice nicely.