At the suggestion of the instrumental pedagogue Egon Saßmannshaus, Bertold Hummel wrote some easy duos for two violoncellos. They can be found in:
 

Egon Saßmannshaus:
Early start on the Violoncello - Volume 2
A violoncello school for children aged 4 and over
Bärenreiter BA9692 ISMN: 9790006536559

Andante (1976)

Presto (1976 )

Autumn Melody (1976)

Musette (1976)

Marcia (1976)

Siciliano (1976)

Autograph score:
Title: Melancolia, Presto, Siciliano, Marcia, Herbstgedanke, Musette - Length: 6 pages - Date: 1976 - Location: Bayerische Staatsbibliothek Munich

Egon Saßmannshaus:
Early start on the Cello - Volume 3
A violoncello school for children aged 4 and over
Bärenreiter BA9693 ISMN: 9790006536566

The sound of horns (1987)

Canon in the lower seventh (1987)

Elegy (1987)

Tango (1987)

Burlesque (1987)

In fifths (1987)

Autograph score:
Title: Burleske, Tango, In Quniten, Elegie, Kanon in der Unterseptime, Hörnerklang - Length: 14 pages - Date: 1987 - Location: Bayerische Staatsbibliothek Munich