Overtonal montage is the fourth type of montage in Soviet Montage Theory. While the other types of montage are straight forward, the descriptions of overtonal montage tend to be vague. While trying to focus on overtonal montage, I learned that it is a combination of the three types of montage that come before it, so I knew I had to try all three of them so that I could better grasp the concept.
Here is the first type, metric montage. With this style, you cute the footage based on time, or to a certain number of frames.
The next type is rhythmic montage. With rhythmic you edit to continuity and manipulate time.
This is tonal montage. In this you cut to elicit a specific feeling from the viewer with the tone of the shots
And finally, overtonal montage. The reason overtonal uses all three is to to bring out an emotion even further, with mild abstraction.