Final answer:
In social studies, a 'generation' usually refers to a period of about 20 to 30 years, which accounts for the time between the birth of parents and their children's birth, and is indicative of generational cohorts in music preferences.
Step-by-step explanation:
The question 'Generations of music listeners are separated by increments of how many years?' does not have a universal answer as it is not a standardized measurement and can vary based on cultural, social, or academic context. However, within the scope of a typical generational gap as studied in sociology, which is often the reference in social studies, a 'generation' is generally considered to be about 20 to 30 years.
This range accounts for the average period between the birth of parents and the birth of their children which could also be seen as the time span between different generational cohorts in terms of music preferences.