Modular synthesis is all about manipulating signals to craft an ephemeral but unique form of art. This chapter deals with a few basic aspects of signal processing that are required to develop modules. A room is an acoustic system that spreads the voice of a speaker. A loudspeaker is an electroacoustic system that transforms an electrical signal into an acoustic pressure wave. Processing a signal with an linear time-invariant system implies the convolution between the signal and the system impulse response. For long signals, it is hard to compute a single discrete Fourier transform (DFT), even when using fast Fourier transform algorithms that reduce the computational cost. A different approach consists of taking slices of the signal and analyzing them with a DFT. The outcome of an improper sampling process or the discretization of a non-band-limited signal results in the leak of spurious content in the audible range, which is undesired.