Notes on coupled oscillators.

For two coupled oscillators there are two distinct frequencies in the motion. These are a function of the masses and spring constants or other factors. How much of each mode shows up depends on how the system is 'launched' (the initial conditions)

It is possible to launch a system so that only one mass is initially moving, then gradually the first one stops and the second one is moving. In this situation, the energy shifts back and forth between the masses.