Certain and uncertain sounds

1 Corinthians 14:7-8  And even things without life giving sound, whether pipe or harp, except they give a distinction in the sounds, how shall it be known what is piped or harped? For if the trumpet give an uncertain sound, who shall prepare himself to the battle?

I used to be a soldier, and every morning there was a certain bugle-sound called "reveille," which means "get up quick"; then a certain other sound of the trumpet meant, "saddle up," and a certain other sound meant, "mount," another very lively one meant, "Forward march." "Now," said Paul, "if a man just gets up and blows a noise out of a trumpet that doesn't signify anything, how can anybody prepare himself for battle?" Therefore he says, "I would rather speak five words to the church with my understanding than ten thousand words in an unknown tongue." 

B. H. Carroll, from An Interpretation of the English Bible, 1 Corinthians 14.