This appendix surveys some of the highlights of developments in spectral audio signal processing, beginning with Daniel Bernoulli's original understanding of acoustic vibration as a superposition of sinusoidally vibrating modes and progressing through more recent history in spectral modeling of audio signals. A complete history of audio spectral models would be a very large undertaking. Instead, this appendix offers a sequence of what the author considers to be interesting and important topics in more or less chronological order.