The Themodist accenting system was invented by a Mr. Crooks who was
connected with the Votey/Aeolian organ company.  E. S. Votey was
credited by Aeolian with successfully applying it to his Pianola,
and later developing it into the Duo-Art.

Some consider it has an intrinsic 'rightness' about it, dividing the
music intuitively into theme and accompaniment rather than bass and
treble.  With well-edited rolls it is capable of the sharpest and
cleanest accents and is astonishingly flexible at the hands (feet) of
a proficient pianolist.

Patents ensured that originally only the Themodist and the Hupfeld
Solodant systems allowed bass and treble accompaniment levels to be
continuously and separately variable independently of the theme.  Other
systems, though often employing rolls cut from Themodist stencils
(masters) but sold under different trade names, had to make do with an
accompaniment level fixed or floating a relative amount below that of
the accented notes.  It is a correctly regulated Themodist/Solodant
that distinguishes Pianolas and Phonolas from ordinary "pumpers".

Paddy Handscombe
London