I've been working with even length audio for a while, so I've had no problem finding the Nyquist frequency in the FFT spectrum, as it's shape is:
$$(\text{dc_component}, f_1, f_2, ..., f_{N/2-1}, f_\text{NYQUIS}, -f_{N/2-1}, -f_{N/2-1}, ..., -f_1)$$
However, an odd number of elements doesn't fit this. What's the layout for odd FFT spectrums?