《晋书·志·第六章》
伏孔有四，为了音高变通时使用。
伏孔四，所以便事用也。
There are four covered holes, which are used when the pitch is changed.
<s>[INST] Convert the following modern Chinese text into Classical Chinese: 伏孔有四，为了音高变通时使用。 [/INST] 伏孔四，所以便事用也。</s>
Convert the following modern Chinese text into Classical Chinese: 伏孔有四，为了音高变通时使用。
user
伏孔四，所以便事用也。
assistant