Definition of positive organ in English:

positive organ

noun

historical
  • A large but movable pipe organ.

    Compare with portative organ
    • ‘William Christie plays modern recreations of old instruments: a two-manual Hemsch-style harpsichord built by Ducornet and Danset, and a positive organ by Johan Deblieck.’

Origin

Early 18th century: positive in the sense ‘adapted to be placed in position’.