Extras include a feature about the painstaking search for suitable dancers from more than 5,000 applicants and a look at the elaborate costumes commissioned.

Drills and grinders often include this feature for added control.

Towards the courtyards they even boasted metal framed glass curtain walls which makes them two of the world's first buildings to include this feature.

Certain keyboards may include a feature that allows the performer to create, compose and customize their own accompaniments.

Later versions did not generally include this feature, and used more conventional surfaces mid-mounted on the fuselage.