THE ROLLER CANARY 87 
describe this as a Kullering Hollow rather than as a 
Knorre. 
Of course, complete harmonious balance between the 
Knorre and this Gluck Hollow or Koller Hollow is the 
ideal of a fine Bass. So soon as the bird opens his beak, 
be it ever so slightly, the tour degenerates, the ground 
tone becomes thereby shallow and nasal, and the con- 
sonants sound sharp and rasping. 
Bass is of great importance in Canary song. All 
breeders are agreed that it is the foundation of the song, 
the bass voice, and it has an agreeable effect upon the 
whole performance, which is pleasing to the ear. It is 
no chance product, but requires careful selection and 
breeding to cultivate and improve upon. ‘The many 
consonants in these tours (rrr, etc.) by their nature 
produce notes that lie deep; they need also to be sung 
uncommonly fast to ensure good tonality. A high- 
pitched bass of good tone does not exist. 
NO SIMPLE MATTER 
For these reasons the cultivation of a deep bass is 
evidently no simple matter. Knorre is of all present-day 
Hollow Tours the deepest, and, so far as the author has 
yet been able to verify, the highest bass lies always about 
an octave to an octave and a half deeper than the deepest 
Hollow Roll. 
Of late years some wonderful variations have been 
developed from Knorre, so that it can certainly be 
regarded as the parent tour of many new forms; it is, 
therefore, the correct thing to reckon it as a fully- 
qualified tour for strain breeders. On account of its 
depth, its wide range of tone, its wonderful capacity 
