Refers to a process of tuning a PA or monitoring system involving the intentional initiation of feedback to locate sensitive or hot frequencies. Monitor systems are most prone to feedback at frequencies where the speakers and/or open microphones have peaks in their frequency response. One can quickly find these peaks by turning up the volume on the mics in question until feedback begins. This is usually where equalization is applied to counteract troublesome frequencies – i.e. if it feeds back at 4 kHz then pull 4 kHz down on your EQ a few dB. Four or five rounds of this is usually enough to get rid of the major problems. While this technique is commonly used for stage monitoring systems, it can also prove surprisingly effective for the FOH system as well, particularly in situations where there is a heavy emphasis on vocal reproduction.