positive organ
A small pipe organ, often portable, used in chamber music or as a continuo instrument in Baroque music.
In Baroque music, the positive organ is often used for the basso continuo.
Variant with interpunct, sometimes used for clarity.
Borrowed from English 'positive organ', itself from the Latin 'positivus' (placed, set up), referring to an organ that is placed on a stand rather than built into a wall.