Matthew Poole and continuators on 1 Corinthians 14:8

8 For if the trumpet give an uncertain sound, who shall prepare himself to the battel? .

The Trumpet is made use of in Battels, and that variously; it is used to give Souldiers notice to march on against the Enemy, and also to sound a Retreat: If there were not a distinction in the one sound, and in the other, how should the Souldier know when to go forward, and when to come back by the sound of it. To instruct them what to do, the Trumpet must not only sound, but sound intelligibly to those that hear it, which it could not, if there were no distinction in the sound.