Frequency response is a subjective criterion that refers to the presence (or absence) of signal in the various ranges of frequencies in the supplied audio and the ratio in which they are present. Musically, it is genre-specific and relates to each sound contained in the recording and the instruments or sound sources used.
For example, some recordings are described as brighter, meaning they contain higher harmonic content at higher frequencies, while others can be described as being darker, sonically. Other classifications of note include the thickness of the sound and its warmth, among others.
Recordings containing electronic sounds typically have a wider and more extreme range of frequencies, both in the upper and subsonic regions of the sound.