A sensing system for a keyboard, the sensing system comprising a plurality of key sensors for respective keys, the sensing system having: a plurality of passive resonant circuits; and a plurality of active resonant circuits, wherein each said key sensor comprises: a said passive resonant circuit, and a said active resonant circuit, the passive resonant circuit having a resonant frequency, the active resonant circuit being configured to excite the passive resonant circuit at the resonant frequency; the sensing system further comprising: at least one sensor driver to drive the active resonant circuits with an RF drive signal equal to or close to the resonant frequency; a multiplexing system to multiplex the drive signal such that simultaneously driven key sensors are separated by at least ( k -1) keys, where ( k -1) is an integer equal to or greater than 1; and at least one detector to detect a level of an RF signal from a driven key sensor, wherein the sensing system is configured to sense a position and/or velocity of a key associated with a driven key sensor as the key moves between key pressed and key released positions, dependent on a said detected level of an RF signal from the driven key sensor. a plurality of passive resonant circuits; and a plurality of active resonant circuits, wherein each said key sensor comprises: a said passive resonant circuit, and a said active resonant circuit, the passive resonant circuit having a resonant frequency, the active resonant circuit being configured to excite the passive resonant circuit at the resonant frequency; the sensing system further comprising: at least one sensor driver to drive the active resonant circuits with an RF drive signal equal to or close to the resonant frequency; a multiplexing system to multiplex the drive signal such that simultaneously driven key sensors are separated by at least ( k -1) keys, where ( k -1) is an integer equal to or greater than 1; and at least one detector to detect a level of an RF signal from a driven key sensor, wherein the sensing system is configured to sense a position and/or velocity of a key associated with a driven key sensor as the key moves between key pressed and key released positions, dependent on a said detected level of an RF signal from the driven key sensor. a said passive resonant circuit, and a said active resonant circuit, the passive resonant circuit having a resonant frequency, the active resonant circuit being configured to excite the passive resonant circuit at the resonant frequency; the sensing system further comprising: at least one sensor driver to drive the active resonant circuits with an RF drive signal equal to or close to the resonant frequency; a multiplexing system to multiplex the drive signal such that simultaneously driven key sensors are separated by at least ( k -1) keys, where ( k -1) is an integer equal to or greater than 1; and at least one detector to detect a level of an RF signal from a driven key sensor, wherein the sensing system is configured to sense a position and/or velocity of a key associated with a driven key sensor as the key moves between key pressed and key released positions, dependent on a said detected level of an RF signal from the driven key sensor. at least one sensor driver to drive the active resonant circuits with an RF drive signal equal to or close to the resonant frequency; a multiplexing system to multiplex the drive signal such that simultaneously driven key sensors are separated by at least ( k -1) keys, where ( k -1) is an integer equal to or greater than 1; and at least one detector to detect a level of an RF signal from a driven key sensor, wherein the sensing system is configured to sense a position and/or velocity of a key associated with a driven key sensor as the key moves between key pressed and key released positions, dependent on a said detected level of an RF signal from the driven key sensor.