A physical implementation of the matrix routing concept, which serves as an alternative to using patch cords to establish signal routing in modular synthesizer and semi-modular models. In a pin matrix, all signals are brought to a set of horizontal and vertical bars mounted behind a grid of holes. Signal outputs are connected to the horizontal bars and inputs are connected to the vertical bars (or vice versa). Inserting a metal pin in a hole establishes a contact between a horizontal bar and a vertical bar, hence establishing a routing.Synths that have used a pin matrix include the EMS VCS3 and the ARP 2500. The pin matrix makes for a much more tidy front panel than the traditional arrangement of patch jacks and cords (which tends to result in patch cords hanging in front of the knobs that one is trying to reach), but this design is also more expensive, takes up more room, and can cause signal quality problems (the ARP 2500 was notorious for signal crosstalk originating in the pin matrix).