Thanks for the replies, av8rmike and MikeS.
Unfortunately, I learned in the brass band, so treble clef was the first thing I learned. I remember the first time I played in an orchestra, with bass clef, I played a C or whatever, and it came out a tone below. The conductor glanced at me, but the glance became a glare after a phrase or two. I was thinking to myself, “Who wrote this garbage?” Much laughter later on though
I’ve never used tenor clef, but it seems from what you’re saying that the secret is just to become good at it, but in your head only have one note name for each position. So in my example above, the open position is always Bb, regardless of clef. However, when coming up against a C in treble clef, I should transpose it a tone down in my head, and play it as a Bb. Sound right?