en_tn_condensed/1co/14/07.md

they do not produce different tones

This refers to sounds of different pitch that make up the melody, not to the difference between a flute sound and a harp sound.

how will anyone know what tune the flute or harp is playing?

Paul wants the Corinthians to answer this themselves. Alternate translation: "no one will know what tune the flute or harp is playing." (See: rc://en/ta/man/jit/figs-rquestion)

tune

melody or song