If you won’t need your pianist for more than five minutes, let them know. Sitting in one position for a long time is uncomfortable, and they may be glad of the opportunity to move around or leave the studio temporarily. At the very least, it means they can relax and know that they don’t have to be looking out for a signal from you for a few minutes.
It’s not a huge issue – it’s no big deal to sit in the corner of the studio when you’re being paid to sit there. But if you can remember to release the pianist when they’re not actually needed, the payoff for the teacher is huge – you’ll get their complete attention when you really need them, and they’ll instantly think of you as someone to collaborate with, rather than to work for.
By contrast, “Oh, I’m so sorry, are you still there? I don’t actually need you” or “Oh what a shame, you could have gone home early if I’d realised” suggests, even if it’s not true, that the pianist and their role is so minimal that you could easily forget they’re there at all, like those people who stand by the doorways in art galleries.
Thank goodness I’m not a dance teacher – I’m sure I’d be terrible at this kind of thing…