A diagnostic procedure carried out before a performance or recording. Particularly when amplified instruments and/or a PA system are used, a sound check is done to ensure that all of the equipment is in working order, and that sound levels are set correctly. A sound check can take the form of a full band performance, or one person moving from mic to mic, instrument to instrument. While it is most commonly used in microphone sound checks, saying, “check one-two-three” into the mic is not really part of the FOH Engineer’s Code. It’s more of a guideline than a hard and fast rule.