Abstract: A synthesizer using the additive method of color synthesis and having a plurality of different color filters to provide corresponding primary color radiations which are combined to produce a tone having a specified color content. The filters are illuminated by either one or a plurality of gas discharge lamps equal in number to the number of color filters, the frequency and duration of the flashes from the lamp incident on each filter being determined by a control circuit to produce a predetermined luminous intensity for each primary color. The circuit may be programmed by specifying numerical values for the required luminous intensity of each primary color and the circuit adapted to control the frequency and duration of the flashes in accordance with the specified numerical values.