Hah! Yes, I didn't want to bring it up, but I was also obliged to
play with both the intro and the ending solo in "Watcher" on the Morazotron, and
while I don't have Bass Accordian either, I substituted the Gothic sound, and it
will curl the hairs on the back of your neck!
We also did "Watcher" and I used the standard Mk2 brass/3 violin but instead of bass accordian (which I don't have), I used the pipe organ, and trust me, if you have it and want a Genesis moment, try it out. Talk about balls.