We often see hidden camera

interviews, they are perfectly legal, because the recorder (person, not the machine) is part of the conversation. The same law applies here also, there is nothing illegal with recording my own speech, and it won't become illegal just because someone else comes in and talks to me as I'm recording myself. The Wire Tap Law is probably (my guess) meant to govern thrid party recordings (i.e., the person doing the record is not party of the conversation).