Abstract: A system and method for automatically detecting and identifying a plurality of frequencies simultaneously present in an audio signal, as well as the duration, amplitude, and phase of those frequencies, then filtering out harmonic components to determine which frequencies are fundamentals. The system includes a computer readable medium of instruction code that decomposes the signal into its component sine waves by computing and comparing correlations between the input signal and sine waves at various phase and amplitude combinations. The system also employs several optimization and error correction routines.