Tools for distinguishing EMG from Beta?

Both EMG and Beta occupy the 15-30 Hz range of the EEG frequency spectrum, at similar power levels. EMG is more broadband and continuous, and Beta is more narrowband bursts. Are there any mathematical tools available to characterize which one is dominant at an electrode at a given time using what is known about the frequency characteristics of each? I know ICA is the preferred solution, but I’m dealing with a limited number of electrodes.

Differences in topography are a good way to go, but that also relies on ICA.

Limited electrodes isn’t a fundamental problem – you can do an ICA with two channels. A limited number of time points would be more detrimental.