Vocal music of the renaissance is almost never sung with vibrato as a rule, and it seems unlikely it ever was; however, it should be understood that "vibrato" occurs over a wide range of intensities: slow, fast, wide, and narrow. Most sources in condemning the practice seem to be referring to a wide, slow, perceptible oscillation in pitch, usually associated with intense emotion, whereas the ideal for modern vibrato, and possibly in earlier times as well, was to imitate the natural timbre of the adult singing voice, from which a measure of vibrato (it has since been shown) is rarely absent.