Fourier series is one way of separating out multiple time-scales, especially when they are regular and periodic. The example I gave will be amenable to that bec

Fourier series is one way of separating out multiple time-scales, especially when they are regular and periodic. The example I gave will be amenable to that because the cycles are very periodic. But the different timescales don't have to be periodic. They can be quasi periodic, or completely irregular. They just have to run at different speeds.