There are 3 versions :
- Dortmund (RH with the cor anglais )
- at 2'10 Wernigerode (RH with the gambe 8')
- at 4'20 Waltershausen (RH with the gorgeous vox humana).
The pitches are those indicated by Reger (eg RH 8, LH 8-4, Ped 16-8)
For Wernigerode, the most obvious choice would have been the free reed clarinette for the RH, but I looked for something else as there was already an excellent version with the clarinette by 24jpr at : http://www.contrebombarde.com/concerthall/music/12472