There is a dance up at Crosby's barn tonight.

[eiris]

There is a dance up at Crosby's barn tonight.I can't understand why the "up" is here.Could you do me a favor?

[cyborg]

There is a dance up at Crosby's barn tonight.I can't understand why the "up" is here.Could you do me a favor?

Dance to be held or
Dance show will be held

[byron]

There is a dance up at Crosby's barn tonight.I can't understand why the "up" is here.Could you do me a favor?

You are correct in your questioning the use of the word 'up' in this way. On the face of it the useage would seem incorrect and unneccessary. However this is a just a case of common useage. It's just the way native English speakers talk. As we all know, there is the way we learn to speak in English from a text book and the way people speak on the street.