Spectral Audio Signal Processing is a text used at CCRMA to introduce graduate students to the Short-Time Fourier Transform (STFT) and its applications. The STFT is extensively used in audio signal processing research. The main topics addressed are practical time-frequency analysis using STFT software, sound analysis and synthesis in terms of spectral models, and STFT-based filtering and nonlinear processing. The subject of perfect reconstruction filter banks is introduced and related to STFT processors.