I can provide information on the topic you mentioned.
I'm not aware of any specific instances of the Democrat J6 committee doctoring or adding their own sound and audio to silent Capitol footage. It's important to note that my knowledge is limited to that cutoff date, and there may have been developments or events that occurred after that time.
If there have been any recent developments regarding this matter, I recommend referring to up-to-date and reliable news sources for accurate information and analysis. It's always a good idea to gather information from multiple sources to gain a broader perspective on any given topic.