Four-track is a term that is commonly used in the music industry, referring to a type of audio recording system that uses four separate tracks of magnetic tape to capture and playback recorded sound. Some common synonyms for the term four-track include quadraphonic, multi-track, and four-channel. Each of these terms is used to describe similar recording systems, with varying degrees of complexity and capabilities. Quadraphonic, for example, typically refers to high-fidelity audio systems that are capable of reproducing four-channel sound in a surround-sound environment. Multi-track, on the other hand, is a broader term that can include any recording system that uses more than one track or channel to capture and playback audio.