This is a grasshopper recreation of a design pattern 'Controller' found in Robert Woodbury's Elements of Parametric Design. In these next 2 definitions, cylinders are manipulated using a series of sliders set up like sound equalizers.
In both definitions, the height of the cylinders are related to the distance between the start points of each cylinder and corresponding points on a set of lines (the equalizer).These points are controlled using the useful 'Point On Curve' components which have been newly introduced (I believe) in grasshopper version 8.0.
In the second definition, a curve is divided in order to get a list of points. This list is fed into one input of the distance component (A), with the other input (B) being fed by the 4 'Point on Curve' components. The list of points (A) must match those in (B) for the 'distance' component to work i.e. a list of 4 points corresponding to another list of 4 points.
The grasshopper definitions can be downloaded here.