The MATHS SUM output adds the four attenuverter-weighted channels, so mixing and subtraction are done by setting polarities

MATHS normals all four Variable Outputs to a central SUM bus: the SUM output is the sum of the four channels’ voltages as scaled and polarised by their attenuverters. Because each attenuverter can invert, the SUM performs not only addition (mixing several modulations into one complex signal) but also subtraction — invert one channel and the SUM computes a difference. The Inverted SUM output flips the whole result for reverse modulation without needing inversion at the destination. Patching a cable into a channel’s Variable Output removes that channel from the SUM (and OR) bus, so only the channels left unpatched are summed.

Examples

Route an envelope through CH1 and an LFO through CH2, both to SUM -> one complex modulation. Invert CH2 relative to CH1 and the SUM becomes their difference.

Assessment

How do you make the SUM output subtract one channel from another rather than add them? What happens to a channel’s contribution to SUM when you patch a cable into its Variable Output?