Ok, I'm not a teenager anymore, but I still get erections all the time.
Most of the time it isn't sexual at all, but it happens.
When you really don't want it to happen, especially in a nervous situation, it happens, and it can be embarrasing if people can see.
I can imagine this is more common than people would admit, and I'm wondering what you all do to prevent it, and to hide it if it happens.
Strategic positioning is a factor, but just as the mind can wander, so can the phallus.
The problem with piano playing is that both hands are in use most of the time, so some awkward bodily shifting might be the only way to hide it from view??