— Voltaire French writer, historian, and philosopher 1694 - 1778
In George Bernard Shaw's Man and Superman, act II, there is the following dialogue:
TANNER: Let me remind you that Voltaire said that what was too silly to be said could be sung.
STRAKER. It wasn't Voltaire: it was Bow Mar Shay.
TANNER. I stand corrected: Beaumarchais of course.
This quote has also been attributed to Joseph Addison. In The Spectator, 21 March 1711 http://www.hoasm.org/VIIA/Spectator3-21-11.html, Addison wrote of "an establish'd Rule, which is receiv'd as such to this Day, That nothing is capable of being well set to Musick, that is not Nonsense."
Fonte: "Nowadays what isn't worth saying is sung" (Aujourd'hui ce qui ne vaut pas la peine d'être dit, on le chante) — Pierre de Beaumarchais, Le Barbier de Séville (1775), act I, scene II.