1) A route leading from one side of the stage to the other, out of the audiences view. 2) An electronic filter in a sound system that routes sound of the correct frequency to the correct part of the speaker system. Different speakers handle high frequencies (tweeters) and low frequencies (woofers). Sometimes known as a crossover network. An active crossover splits the signal from the mixing desk into high, mid and low frequencies which are then sent to three separate amplifiers.