1 Corinthians 14:7-9

7Yet even lifeless instruments, whether flute or harp, in producing a sound, if they do not produce a distinction in the tones, how will it be known what is played on the flute or on the harp?

8For if 1the trumpet produces an indistinct sound, who will prepare himself for battle?

9So you too, unless you produce intelligible speech by the tongue, how will it be known what is spoken? For you will just be 2talking to the air.