[Tim Mariott]

Can anyone suggest how I might be able to represent in Notation the feature that I have circled at the bottom of the attached page?

I know how it sounds - a set of "rumbling" octaves - and I'm sure it has a fancy name but I cannot work out if I can input it into Notation.

I don't need it to play properly as my requirement is to input the score so that I can transpose it for my accompanist.

If all else fails I will just leave these measures blank and manuscript it into the printed score after transposing.

Thanks for any help.
Tim