Organ in the Aa-kerk in Groningen

The Der Aa-kerk in Groningen in the Netherlands was built in its current cruciform shape in the late Gothic period, and was named after the neighboring river Aa.

For example, the facade pipes were made of pure East Indian tin and the bass octave had all twelve semitones.

The case for the new organ was made by Allert Meijer and by Schnitger and the carving was by Jan de Rijk.

[3] Nicolaas Arnoldi Knock recorded the disposition of the Schnitger organ in the Academiekerk in 1788, reflecting the situation after work by Hinsz in 1784 (Knock's disposition is missing the Octaaf 4′ in the Rug-Positief):[4] The Rugpositief case reflects the main case in scaled-down form.

The Borstwerk doors have openwork acanthus carving and feature two double-headed eagles from the Groningen coat of arms.

The gallery (brought from the Academiekerk) had to be redesigned, and also the wide entrance-portal below, with its three double-winged doors under round arches, made by furniture-maker (and later city master-builder) Allert Meijer, who created Schnitger's organ cases in the Groningen area.

[3] Because the six wedge bellows were placed behind the organ, and because the gallery is less deep than in the original location, the space for the organist between the console and Rugpositief was significantly reduced.

Four music-making cherubs from 1815 crown the Rug-Positief and female figures and angels with musical instruments top the main case.

Wallis also replaced the original carvings beneath the side towers of the main case with two near-life-size figures of Atlas.

In 1856–58 the instrument was remodeled by Petrus van Oeckelen of Groningen, and adapted to the taste of the time by enlarging the Hoofdmanuaal from 9 to 13 stops on new windchests, adding three more stops to the pedal in the lower case, and adding the missing C sharp and D sharp to the bass octave.

In 1990 the organ was partly restored and rebuilt by the Reil firm of Heerde, including Schnitger's wind-chests.

The expert Rudi van Straeten created a restoration proposal in 1993, using the state of 1858 as a base, but with some technical improvements.

Two arguments were made strongly for maintaining the grown state: first, there was no serious structural instability (which had been feared), and second, the special sound qualities of the instrument as extant should not be lost.

The organ is praised for its singing Praestants with their subtle response, its colourful flutes, and rich-toned reeds that enable a wide variety of combinations.