In signal processing, the production of a signal by manipulating time domain and/or frequency domain elements. Additive synthesis is the generation of a complex signal by adding together individual sine-wave components. The resulting signal is usually a periodic waveform and the sine-wave components are therefore harmonically related as integer multiples of the fundamental frequency. Subtractive synthesis uses spectrally rich raw signals from which components are removed, usually by means of filters. FM synthesis is a process that makes use of the frequency modulation (FM) technique.