Singverein <Krefeld>
| Georg Werner an Louis Spohr in Kassel | Düsseldorf, Donnerstag 9. November 1826 | 1826110915 |
| Heinrich Scheibler an Louis Spohr in Kassel | Krefeld, Freitag 10. November 1826 | 1826111047 |
| Georg Werner an Louis Spohr in Kassel | Düsseldorf, Donnerstag 9. November 1826 | 1826110915 |
| Heinrich Scheibler an Louis Spohr in Kassel | Krefeld, Freitag 10. November 1826 | 1826111047 |