A signal processing system, a signal processing apparatus and method, a recording medium, and a program in which high frequency components of a narrow-range signal having suppressed high frequency components can be restored with high accuracy. A narrow-range audio signal having low frequency components is divided into frames by a frame-unit dividing unit, and is spectral-transformed into a signal on a frequency domain by a DCT transform unit. A learning-produced-data table extracts, at an address corresponding to a class code supplied from a classifying unit, high-frequency-component DCT spectrum data. In a spectrum combining unit, the extracted high-frequency-component DCT spectrum data is combined with low-frequency-component DCT spectrum data output from the DCT transform unit. Subsequently, a broad-range audio signal having combined high frequency components and low frequency components is output.