And yet another way... 2013

Create a wav file of just the drums without the pushes.

Create another song, chords don't matter for drums, mute everything except the drums. (Solo the drums track). Put in the same numbers of measure but just don't add the pushes.

Render this drum only song to a wave file.

Put the wav file in the same folder as the .MGU and name it the same as the song but add "drums" onto the end.

If the song name is
Yet Another.mgu

Name the drum only wave file as
Yet Another Drums.wav

The "Drums" indicator will change from Green to Orange.

When you play, Band in a box will play this wav for the drum track.

It actually tracks tempo changes in BIAB

Very handy feature!

This works for other tracks. "Piano", "Bass" etc.

It also works if you create a general wav for all the tracks.

For example Render a few tracks to:
Yet Another.wav
And you'll be able to stack in more tracks.