Rick The 120Hz refers to the general screen refresh rate of animations, like the moving indicator and strobe. With 120Hz these animations appear buttery smooth. This is however purely cosmetical. But for me it is easier on the eyes if I have to look on a display for hours.
One should not confuse this with the analysis frequency: the rate at which pianoscope analyzes and updates the measured values. This is currently fixed at about 7Hz. This is fast enough for all practical purposes. I once experimented with a higher analysis frequency which makes pianoscope react extremely smooth to all pitch changes. But it comes at the cost of a far higher energy consumption. On the most modern iPhones it should however be possible to double or even triple this frequency. Perhaps I will add an option for this in the future.