“Let freedom ring, unless it's on vibrate.”

[Brother Theodore Complete Collection on Letterman, 1982-89, Don Giller, https://www.youtube.com/watch?v=kj5fVnHWUl4]

Comment after the match with Jimmy Ellis was stopped by the referee in the twelfth round (July 1971)

Variations of this quote are often attributed to Stevenson without a date or location for the remark. Two early occurrences are in a Congressional hearing on November 13, 1985, where Stevenson was quoted by Representative Ted Weiss ("Limits on the Dissemination of Information by the Department of Education" (1986), published by the GPO); and an article dated June 4, 1989 by Sue Ann Wood in the St. Louis Post-Dispatch ("Write Editor, Readers Urged"). No source closer to Stevenson has been found.
Disputed

America, reported in Bartlett's Familiar Quotations, 10th ed. (1919).

Spoken prelude
Atlantis (1968)

Lift Every Voice and Sing, st. 1 (1900).

Section 3 : Work Democracy versus Politics. The Natural Social Forces for the Mastery of the Emotional Plague;
Variant translation: The cry for freedom is a sign of suppression. It will never cease as long as man feels himself to be trapped. No matter how different the cries for freedom may be, at bottom they always express one and the same thing: the intolerableness of the organism's rigidity and the mechanical institutions of life, which are sharply at variance with the natural sensations of life. ... Not until man acknowledges that he is fundamentally an animal, will he be able to create a genuine culture.
The Mass Psychology of Fascism (1933), Ch. 10 : Work Democracy
Context: The cry for freedom is a sign of suppression. It will not cease to ring as long as man feels himself captive. As diverse as the cries for freedom may be, basically they all express one and the same thing: The intolerability of the rigidity of the organism and of the machine-like institutions which create a sharp conflict with the natural feelings for life. Not until there is a social order in which all cries for freedom subside will man have overcome his biological and social crippling, will he have attained genuine freedom. Not until man is willing to recognize his animal nature — in the good sense of the word — will he create genuine culture.