Keyboard matrix circuit

For example, 16 wires arranged in 8 rows and 8 columns can connect 64 keys—sufficient for a full five octaves of range (61 notes).

By determining the timing between the activation of the first and second switches, the velocity of a key press can be determined—greatly improving the performance dynamic of a keyboard.

The second is that instruments with a matrix circuit can only play in a monophonic fashion without the addition of a diode for each key crossing.

[1] Monophonic instruments and most low-cost computer keyboards reduce costs by leaving out most or all of those diodes.

[3][4] Often in pocket calculators the multiplexed digit drive lines would be used to scan the keyboard as well, providing further savings.

The inside of a Yamaha SY77 synthesizer shows the various internal components. The switches for each key are connected to the microprocessor chip using a matrix circuit. Even though the SY77 has 61 keys, only two small ribbon cables of wiring comes from the keyboard matrix.