1 Corinthians 14:6-8

6Now, believers, if I come to you speaking in unknown tongues, how will I benefit you unless I also speak to you [clearly] either by revelation [revealing God’s mystery], or by knowledge [teaching about God], or by prophecy [foretelling the future, speaking a new message from God to the people], or by instruction [teaching precepts that develop spiritual maturity]?

7Yet even lifeless things, whether flute or harp, when producing a sound, if they do not produce distinct [musical] tones, how will anyone [listening] know what is piped or played?

8And if the [war] bugle produces an indistinct sound, who will prepare himself for battle?