The backbone operations of modular synthesis are addition, subtraction, attenuation and inversion of signals. LVL excels at each of these operations, providing two identical manually controlled voltage summators: one on the left half, and the other on the right half of the module.

Each summator has three inputs. The inputs are DC coupled, meaning they will not block the constant component of the incoming signal, making the module suitable for audio, CV and any other type of a signal existing in a Eurorack system. Each input has an associated level control. The knobs follow the order of the inputs, i.e. the topmost knob is associated with the topmost input of the selected summator.

A switch to the right of the input jacks sets the summator's mode. In up position (-+), the level knob will act as an attenuverter. In this mode, the input signal will pass to the output at maximum level if the associated knob is set fully clockwise. As it is turned towards noon, the level is decreased and reaches 0 (no signal passes through) at noon. Then, as it is turned towards the full counter-clockwise position, the inverted version of the input signal will reach maximum. So if the input is a falling sawtooth from 5 to 0 volts and the level control for this input is fully CCW, a rising sawtooth from -5 to 0 volts will appear at the output. If the mode switch is in the down position (0+), the level controls act as simple volume knobs, with no signal passing through when full CCW and maximum signal level at full CW. This mode may be preferrable for audio mixing, since sometimes it's necessary to quickly fade out a particular sound, and it's not always easy to hit the exact middle point in -+ (attenuverting) mode. The attenuverting mode makes sense when summing CVs or trying to tap into more experimental audio summation, e.g. subtracting the filtered signal from the unfiltered.

LVL features clever normalling of signals. Every input of the left summator (Summator 1) is normalled to respective inputs of the right summator (Summator 2). That is, if nothing is connected at a summator 2 input, but something is connected to the same input on Summator 1, a copy of that signal will appear automatically at the corresponding Summator 2 output. This way, one could use LVL as a mini matrix mixer! If only Summator 1 inputs are used, the Summator 2 inputs will simply copy whatever is going on on the first summator inputs. Naturally, the level controls on the two summators are independent, so one can easily achieve two different mixdowns of up to three different signals using this feature. It is, of course, possible to use this feature for just two channels, for example, and put something else into the third input of summator 2: summator 1 will then output its own inputs' sum, and summator 2 will process two inputs of summator 1, and a signal that was patched directly to it.

Finally, a constant voltage of +6v is normalled to summator 1 lowest input (input 3) jack. So, if nothing is patched to summator 1 input 3, its blue knob will effectively become an offset generator of -6...6 (-+ mode) or 0..6 (0+ mode) volts range. Summator 2 will receive this offset into its own input 3 only if nothing is patched into both Summator 1 and Summator 2 input 3. So, if you know you are going to need all three inputs of LVL, it may be logical to start with Summator 2, as to keep the other half's offset functinoality for possible use later on in patch building.