Teaching Music Technology brings back additive synthesis, year by year. For some students the concept of every harmonic sound being a multitude of frequencies is hard to grasp. Visualizing it is always a good way of crarifying things. FS/Partial would come in handy during those lessons.
FS/Partial is an instrument created by Dogo Tudela and is meant as a visual way to perform additive synthesis in live contexts. Eight partials can be controlled by the user, by pushing the columns up and down, increasing and decreasing the volume of the sine waves: