there are some programs that do like students to audition but these tend to be smaller programs and they would have formal advanced clerkships or sub-i's to take if that were the case. in general, it is not required. it can be helpful to do an away somewhere if you come from a lesser known school in order to get good LoRs. However, doing away rotations appear to hurt more than they help from what I have seen. they are best seen as a chance to audition the program, than for you to audition yourself.