I report on the electrochemical tuning of the plasmon resonances of single and strongly coupled gold nanoparticles. I combined hyperspectral dark field imaging, cyclic voltammetry, and single particle scattering spectroscopy in a purpose-built custom instrument to investigate the electrochemical sensitivity and tuning mechanisms of surface plasmon spectroscopy. Cyclic spectrovoltammetry showed that single gold nanospheres show localized surface plasmon resonance shifts and damping correlated to the total charge of the particle in accordance with recent reports by Dahlin et al. Very strongly coupled nanoparticles show a much more complex spectrovoltammetric dependence, exhibiting behavior nearly opposite that of single particles. This suggests a much larger role of surface complexation in spectroelectrochemical tuning than is assumed in the literature. These results will impact the fundamental understanding of noble metal nanoparticle-solvent interfaces and interactions, development of ultrasensitive plasmon based electrochemical sensors, and a means to explore previously unmeasured optical properties of gold halides.