The Moog modular system consists of a number of various modules mounted in a cabinet. Each module performs a specific signal-generating or -modifying function. These modules offered unprecedented control over creating sounds by allowing a user to modify primary sound waveforms (sine waves, square waves and other waveforms provided by voltage controlled oscillators or VCO) with amplitude modulators (voltage controlled amplifiers or VCA) and spectral modulators (voltage controlled filters (VCF) or fixed filter banks) and other modifiers. Envelope generators provided further control by modulating the attack, decay, sustain and release (ADSR) parameters of the VCAs, VCFs and other modules. The modules are patched together with patch cords with ¼-inch mono plugs. The patch cords and module parameter knobs could be adjusted in countless ways to create a nearly infinite number of sounds. The final sound was heard ('triggered') from the system by pressing a key on an attached keyboard or pressing on the ribbon controller.