Jan Templin askes the musical question:

>...  Or more generally, what is used for performances of such music in
>venues without an organ?  An electric instrument?  Is there such a thing
>as a portable organ?

I attended a performance of the Well Tempered Clavichord at the Gardner
Museum in Boston, given by Robert Levin.  Levin played piano, harpsichord,
clavichord and small portable organ, using what he considered the most
suitable instrument for each prelude and fugue.  As I remember, he
conceded that the organ was not on the level of a "real" organ. It
was not an electric instrument.

Professor Bernard Chasan
Physics Department, Boston University