Sonus paradisi Polna organ by J. D. Sieber 1708

The Sieber organ for Polná was his fourth largest instrument, and it was perfectly preserved in original form through to the present. Jürgen Ahrend studied the Polná instrument carefully when reconstructing the Sieber organ in Vienna (1986–87). The organists of Polná still remember that Ahrend restored the resonators of the pedal Trumpet in Polná in the gratitude for the research he could conduct there.

The organ was neatly overhauled by a consortium of Czech organ building companies in 2017. The companies were: MgA. Dalibor Michek (Puklice - Studénky u Jihlavy), Dlabal - Mettler (Bílsko u Olomouce), and MgA. Marek Vorlíček (Domažlice). The organ was dismantled and transported to the various organ workshops. The case of the instrument remained on the site, restored by Jan Mach from Červený Kostelec. The organ was heavily infested by wood-eating insects. Although according to the restorers, it was fortunate that it was worms and not humans that did most of the damage. Although the parts were dilapidated and worn, they were preserved in a very original (unchanged) condition. The original fifth comma mean-tone temperament could be identified and the organ re-tuned. The manual keyboards turned out to be the original Sieber keyboards, which is truly unique for an organ this old. These are some of the oldest surviving keyboards in the Czech realm. According to Martin Lexa on the website of the Polná parish, it was possible to restore the original winding: four large wedge bellows located in the church tower.