A method of signal routing within a synth in which interconnections between sources and destinations are arranged on a grid, which may be conceptual or physical. In the matrix concept, modulation signal sources (e.g., an LFO) are placed on horizontal lines on the grid, and destinations are placed on vertical lines (or vice versa). Each place where a horizontal and a vertical line intersect, the respective source and destination can be connected together.
The matrix concept is physically implemented by the pin matrix, as used on the EMS VCS3 and the ARP 2500. It can also exist in software, or in analog circuitry by the use of an integrated circuit known as a "bilateral switch". The Oberheim Matrix series implement matrix routing as a virtual concept; the performer can select from a list of sources and destinations, place an interconnect on a source-destination pair, and set the signal level which is to be passed through the interconnect.
In theory, matrix routing allows everything to be connected to everything else, but there are practical limits. The Oberheim Matrix synths have hardware and software limits on the total number of interconnects that can be active at one time. Pin matrix routing has problems with impedance matching and loading down of signal sources, if a signal is routed to too many destinations, or if too many sources are combined on a destination.