The Riddagshausen instrument has been well demonstrated but as it is not heard often at present here are two short pieces by different composers. They are #80 and #1 from
http://conquest.imslp.info/files/imglnks/usimg/f/f3/IMSLP504046-PMLP816638-Postludien.pdf
The first by Pachaly (1797-1853) is with a soft registration.
The second by Georg Armbrust (1818-1869) starts soft and gradually builds to FF. If you think this sounds chromatic there are 126 accidentals in the 55 bar piece.
Armbrust when organist of St Peter's Church in Hamburg knew Brahms and this get a mention in an interesting book The Organ Music of Johannes Brahms by Barbara Owen published by OUP in 2007.