We propose a new algorithm to compute the frequency modulation functions associated with the well-known monogenic signal. The new algorithm extracts the frequency modulation functions with-out requiring an auxiliary process to estimate local orientation. In addition, we show that, in situations where a multi-scale multi-orientation decomposition is required to analyze a signal, the partial Hilbert transform approach computes AM-FM functions similar to those obtained by the monogenic signal while maintaining a more efficient signal representation. Index Terms — AM-FM, monogenic signal, partial Hilbert transform 1