1 Corinthians 14:7-8

14:7 It is similar for lifeless things that make a sound, like a flute or harp. Unless they make a distinction in the notes, how can what is played on the flute or harp be understood? 14:8 If, for example, the trumpet makes an unclear sound, who will get ready for battle?

1 Corinthians 14:11

14:11 If then I do not know the meaning of a language, I will be a foreigner to the speaker and the speaker a foreigner to me.