If you are using Windows 7 or earlier no concerns.
If using Windows 8.1 and capturing music for example and when capturing your music contains your screen reader's synthesizer's speech output in these music recordings then do the following,
When recording has started turn off your screen reader application with JAWS its insert+F4 then choose ok then when done recording start JAWS with your hotkey. Mine is ctrl+alt+j
If you use NVDA to turn off NVDA speech use insert+q then choose ok. When done recording simply press your hotkey which is usually ctrl+alt+n.
This method will not record your synthesizer's speech output.
Your music will only get recorded.
Exceptions will be the first recording and last recording.
It's a good idea to turn off all other applications like email, Skype and other programs that may make sounds. Also, if you have scheduled scans set up and if these programs make sounds then reschedule these programs to scan at a different time and not when you are recording.
It's a Windows 8 thing.