Abstract: A digital signal mixing device comprises a plurality of input channels (29, 30, 31, 32, 33) each having a respective signal input port (34, 35, 36, 37, 38) for analogue signals, an interface circuit (49) incorporating an analogue-to-digital converter, digital signal processing means (51, 66, 52, 50) for conditioning the digital signal to effect for example volume control, tone control and introduce other musical effects, and summing means (55) interconnecting the individual channel with next adjacent channels upstream and downstream thereof in a sequence such that mixing of the signals is effected by successive addition of the conditioned digital signals produced by an input channel to a signal representing the addition of the output signals from all input channels earlier in the sequence.