The sound of a musical instrument can be represented either in time domain (envelope, waveform) or in frequency domain (spectrum, harmonics). The variation of the spectrum is analysed as a function of the sound length, the envelope and the oscillations in amplitude and frequency (vibrato). Different types of signals are considered, both electronic and from real instruments. Nuño Fernández, L. (2018). Acoustics for Musicians: Sounds & Spectra. http://hdl.handle.net/10251/104574