《史记·八书·乐书》
于是召见乐师名叫涓的人，对他说道： 我听到了抚琴的声音，问身边的从人，都说没有听到。
乃召师涓曰： 吾闻鼓琴音，问左右，皆不闻。
He then summoned the music master Pian, saying to him, "I heard the sound of the zither. I've asked people following me and they all said they didn't hear anything."