I wouldn't record my session, whether or not my T knew or not, because being recorded just makes me nervous and I never feel "natural" when I know I'm being recorded (not to mention the whole hating the way my voices sounds on recordings thing). It would feel more like a performance than a genuine session. (I think that's a throwback to being a musical performer. Knowing you are being recorded raises the awareness of trying to give your "best" performance, not your "usual" performance.) I think I'd end up with a recording of a session where I felt very inauthentic and intimidated the whole time which would essentially mean the recording would be pretty much useless to me.