Control signal generating apparatus generates a first plurality of output signals (SIG-1 and SIG-2) from a second plurality of input signals. For each output signal, locus generating means (12-1, 12-2, etc.) define a sequence of combinations of values corresponding to the input signals forming a line-like locus in the space defined by the input signals; and for each locus generating means, there is a distance value signal calculator (13-1, 13-2, etc.) for evaluating an output signal having a value determined by the distance in said space of the point (the cursor point) represented by the combination of input signal values relative to the locus. The distance value is the distance along the locus corresponding to the projection of the point onto the locus. Setting means adjust the loci defined by the locus generating means. An input device (10) is controllable by an operator to generate the second plurality of input signals; a display device (11) displays the cursor point and, for each locus generating means, the locus defined thereby and, on each locus, the projection of the cursor point onto that locus. The input device may include switch control means. To compress a set of variables corresponding to the number of output signals, the set of variables is displayed, the set of output signals is also displayed, the set of variables is compared with the set of output signals, and the input signals (which are fewer than the output signals) are adjusted to reduce the difference therebetween so that they represent the set of variables.