A souncheck is an activity that takes place before a concert, speech or similar performance, when the performer and the sound crew run through a small portion of the upcoming show to make sure that the sound in the venue is clear and at the right volume and tonal frequencies. Soundchecks are especially important for popular and other musical genres that use heavily-amplified PA systems; having correct sound is crucial to the success of such events. A soundcheck remains part art and not all science, however, because the acoustics of a venue often change somewhat once it is filled with an audience.