In my experience, it’s always a compromise between what the caller asks for and what the band knows and are happy with. In days gone by, dance bands tended to play from notation, and could render any tune if they had the dots to follow, whereas now most of us either play from memory or by ear, making it more difficult to offer tunes we don’t already know. When calling for dances, I either have to suggest appropriate tunes that the others know, or think of another dance altogether, given that some dances like the Playford ones are so associated with particular tunes that it’s almost unthinkable to try another tune for them.