Mammut is a program for Linux, Windows and Mac that do sound processing in the frequency domain. The program makes an FFT, a “fast Fourier transform” of sound in its entirety. Various operations can then be done in the frequency domain, such as non-linear stretching of the spectrum and spectrum shift. Mammut is a rather unpredictable program, and the user must get used to letting go of control over the time axis. The sounding results are often surprising and exciting. Mammut is also ideal for common operations such as filtering, spectrum shift and convolution and it provides an optimal performance.