Does anyone have any tips for accompanying other instruments? I've stupidly agreed to accompany my brother for his trumpet exam. I can play the accompaniment fine on my own, but it is very hard to follow my brother, as he varies speed hugely (and ignores my complaints).
I've played on other instruments in numerous orchestras and bands, so I'm used to playing with other people, just never have on piano before. I'm not sure if its because I'm reading two lines of music and trying to concentrate on the trumpet as well.
Any advice would be greatly welcomed!

Perhaps a metronome could help?

I tried to accompany my school choir, and the choir's accomanist was my piano teacher, so when I was good enough with the piece, I asked her, and she told me that If I wanted to accompnay something, that I need to 1. have the piece basically memorized, and 2.) Go with the flow of the other group. In this case, your brother. When I went to play with the conductor conducting, I found out that I still needed alot of work. you might know how to play the piece, but let your brother set the tempo, and watch him for all of the changes. I wish you best of luck.