We are now finished developing the mathematics of the DFT and a first look at some of its applications. The sequel consists of appendices which fill in more elementary background and supplement the prior development with related new topics, such as the Fourier transform and FFT algorithm.
For further study, one may, of course, continue on to Book II (Introduction to Digital Filter Theory [71]) in the music signal processing series (mentioned in the preface), or skip filters and proceed to Book IV on Spectral Audio Signal Processing [73]; the chapters starting with ``Spectrum Analysis of Sinusoids'' are focused on practical FFT usage. Alternatively and in addition, the references cited in the bibliography can provide further guidance.