《旧唐书·列传·卷九十九》
及至制作完毕，皇上临殿亲自试验敲击，皆合于五音，群臣称贺。
及事毕，上临殿亲试考击，皆合五音，群臣称庆。
When the production was completed, the emperor personally tested the instruments by striking them in the hall. They were all in accordance with the five tones, and the courtiers congratulated him.