Control device (10, 20, 30) for controlling a customizable audio-visual effect, which comprises: - means for generating at least two first optical paths followed by non-parallel light beams (110a, 110b, 210a, 210b, 210c, 310a, 310b, 310c), which paths comprise at least one optical sensor (115, 215a, 215b, 315a, 315b, 315c) and at least one emitter (105a, 105b, 205a, 205b, 305a, 305b, 305c) of at least one light beam, - means (145, 245, 345) for measuring the speed (150, 250, 350) of an object successively crossing at least two rectilinear light beams as a function of a signal (120, 220a, 220b, 320a, 320b, 320c) exiting from at least one optical sensor representing the absence of light successively on the optical paths due to each optical path being crossed by the object, - means (125, 225, 325) for estimating the longitudinal position (130, 230, 330) of the crossing of the light beams by the object, as a function of a length of time, called the "transit time", between two instants characteristic of a signal coming from at least one optical sensor representative of the absence of light from at least two light beams due to the optical paths being cut successively by the object, and - control means (135, 235, 335), called "positional control means", for controlling a parameter value (140, 240, 340) of an audio-visual effect as a function of the estimated longitudinal position; characterized in that: - the means for measuring the speed of the object are configured: to determine, for at least one beam, the length of time, called the "interruption time", during which the beam was not captured by the optical sensor, and to divide a predefined dimension d of the object by said interruption time, or, the generating means also generating an additional optical path followed by a light beam, parallel to one of the first optical paths, between an optical sensor (115, 215a, 215b, 315a, 315b, 315c) and an emitter (105a, 105b, 205a, 205b, 305a, 305b, 305c) of at least one light beam, to divide the distance between two parallel light beams (210a, 210c) by the transit time between these two parallel light beams, - the means for estimating the longitudinal position of the object's crossing of at least two non-parallel light beams are configured to multiply the object's transit time between two non-parallel beams by the speed measured. - means for generating at least two first optical paths followed by non-parallel light beams (110a, 110b, 210a, 210b, 210c, 310a, 310b, 310c), which paths comprise at least one optical sensor (115, 215a, 215b, 315a, 315b, 315c) and at least one emitter (105a, 105b, 205a, 205b, 305a, 305b, 305c) of at least one light beam, - means (145, 245, 345) for measuring the speed (150, 250, 350) of an object successively crossing at least two rectilinear light beams as a function of a signal (120, 220a, 220b, 320a, 320b, 320c) exiting from at least one optical sensor representing the absence of light successively on the optical paths due to each optical path being crossed by the object, - means (125, 225, 325) for estimating the longitudinal position (130, 230, 330) of the crossing of the light beams by the object, as a function of a length of time, called the "transit time", between two instants characteristic of a signal coming from at least one optical sensor representative of the absence of light from at least two light beams due to the optical paths being cut successively by the object, and - control means (135, 235, 335), called "positional control means", for controlling a parameter value (140, 240, 340) of an audio-visual effect as a function of the estimated longitudinal position; - the means for measuring the speed of the object are configured: to determine, for at least one beam, the length of time, called the "interruption time", during which the beam was not captured by the optical sensor, and to divide a predefined dimension d of the object by said interruption time, or, the generating means also generating an additional optical path followed by a light beam, parallel to one of the first optical paths, between an optical sensor (115, 215a, 215b, 315a, 315b, 315c) and an emitter (105a, 105b, 205a, 205b, 305a, 305b, 305c) of at least one light beam, to divide the distance between two parallel light beams (210a, 210c) by the transit time between these two parallel light beams, to determine, for at least one beam, the length of time, called the "interruption time", during which the beam was not captured by the optical sensor, and to divide a predefined dimension d of the object by said interruption time, or, the generating means also generating an additional optical path followed by a light beam, parallel to one of the first optical paths, between an optical sensor (115, 215a, 215b, 315a, 315b, 315c) and an emitter (105a, 105b, 205a, 205b, 305a, 305b, 305c) of at least one light beam, to divide the distance between two parallel light beams (210a, 210c) by the transit time between these two parallel light beams, - the means for estimating the longitudinal position of the object's crossing of at least two non-parallel light beams are configured to multiply the object's transit time between two non-parallel beams by the speed measured.