Yesterday I was doing some work on intonation using a tuner app on my smartphone. I played a Bb with my eyes closed trying to make my best tone. (This was with the tuner app turned on.) Then, with the tone still being held, I opened my eyes and checked the tuning position indicator. (I will just call it the needle, though that's not really what it looks like.) Then I changed the main tuning slide and did it again. I repeated this several times with different tuning slide positions, sometimes quite different positions.
Now here's the surprising part. The tuning slide position very little difference in the pitch I produced. When I opened my eyes to look at the position of the needle I was almost always about 10 cents above Bb, almost regardless of the tuning slide position.
This makes no sense to me. I don't think that my ear is good enough that I was remembering the old pitch and subconsciously lipping the note to the (nearly) exact same pitch regardless of the tuning slide position, and yet that's seems to be what the empirical result seems to be indicating.
Can anyone give me some insight about this odd and surprising result? Have any of you had a similar experience?