Beat detection usually work by taking the Fourier transform of the signal, and by observing the changes around 100Hz (the frequency where the kicks are, usually

Beat detection usually work by taking the Fourier transform of the signal, and by observing the changes around 100Hz (the frequency where the kicks are, usually, may need tuning). By observing the changes in frequency, one can 'detect beats'. The 'hard' part here is to compute the Fourier transform (which can be both a hard maths and performance problem for a person who knows nothing about signal processing), but quite a few implementations exist in javascript already (plus, if the author uses the new typed arrays, it brings a nice speed boost).