Analog switches are a solid state alternative to relays, when you want a smaller, lower-power technology that won't wear out mechanically. And, as the name implies, you can use the Adafruit ADG729 Dual 1-to-4 Analog Matrix Switches to connect between two sets of four analog signals, much like 8 mechanical switches. These chips tend to be tiny surface mount parts, so this breakout will let anyone use the ADG729 switch for signals up to 5V, without fiddly soldering.The ADG729 uses I2C to select which of the 8 channels switches to turn on or off. Four channels connect to the DA analog pin, and the other four channels connect to the DB analog pin. Note that unlike digital switches and multiplexers, these are not 'input' and 'output' because the signal is bidirectional. You could have the DA or DB signal be an input to 4 outputs, or the 4 inputs to one output.