It is sometimes stated that Key was himself a prisoner, during the bombardment, on a British warship.

That is a mistake.
By a curious coincidence, only a few minutes after my pamphlet had reminded me of the origin of "The Star-Spangled Banner" here in Baltimore, I heard the air played under circumstances very different from any which could have been anticipated by the author of the poem, or the composer who set it to music.
The entertainment at the Academy that night was supplied by an elaborate "show" of the burlesque variety known as "The Follies," and it so happened that in the course of this hodgepodge of color, comedy, scenery, song, and female anatomy, there was presented a "number" in which actors, garbed and frescoed with intent to resemble rulers of various lands, marched successively to the front of the stage, preceded in each instance by a small but carefully selected guard wearing the full-dress-uniform of Broadway Amazons.

This uniform consists principally of tights and high-heeled slippers, the different nations being indicated, usually, by means of color combinations and various types of soldiers' hats.

No arms are presented save those provided by nature.
The King of Italy, the Emperor of Austria, the Czar, the Mikado, the British Monarch, the President of France, the King of the Belgians, the Kaiser (for the United States had not then entered the war), and, I think, some others, put in an appearance, each accompanied by his Paphian escort, his standard, and the appropriate national air.
Apprehending that this symbolic travesty must, almost inevitably, end in a grand orgy of Yankee-Doodleism, I was impelled to flee the place before the thing should happen.

Yet a horrid fascination held me there to watch the working up of "patriotic" sentiment by the old, cheap, stage tricks.
Presently, of course, the supreme moment came.