What am I doing wrong.
Every time I change the drumfils, A, B, C and D, I have to save the song and reopen it again before I can hear the changes. That doesn't seem right.

Saving the song file is half the battle. The other half of the battle is to have Band-in-a-Box regenerate the tracks so the changes are implemented.

When you close the program, open the program and load the song file you are effectively having the program regenerate the tracks.

To hear your changes after saving click the regenerate and play button.

so easy, thank you