"I figured it out! The NCH instructions are wrong (or at the very least, misleading). Set up for recording by clicking on the red button or use F5. The "record control" pop up box will appear."
NCH training video still shows the Record Control popup when record is selected.
E.g. 3 minutes into this intro video:
http://www.nch.com.au/wavepad/tutorial.html#start
However, newer versions of Wavepad (since v5.29) there is no "record control" pop up window.
This was previously mentioned in this WavePad forum post:
http://nch.invisionz...record +control
Instead, before recording, go to options, recording (e.g., see screenshot ) to make your selections then do your recording.
