The device pictured is a scope being used as a frquency county. This is bening used to check the tunning of ocilators of a particuler synth. keith emerson has one on top of moog modular synth and all members had them on their modular systems as well. Thfrequicy counter of the scope makes it faster to tune synthesizers in a live situation. The scope will to what frequencies on in tune and which ones are not and by how munch. In the 70's and early 80's this was a must have in both studio and in live situations
