The important item here is the complete set of the Op 33 songs. Only the second song of the Op 33 set, Våren ('Last Spring'), has had many takers – Schwarzkopf and Tauber among them.
The rest are lucky to have a single recording in the catalogue, if that.
Grieg had been recovering from the deaths of his parents and was going through a bad patch in his marriage when he set 12 poems by AO Vinje for his Op 33 set, hence their preoccupation with darker themes of mortality and mankind.
Groop does well by them, making full use of her deep mezzo colouring. Her singing is beautiful, sympathetic, typically bringing a sense of calm and understanding to 'The Spring' ('Våren') and stretching to the weightier seriousness needed for a song such as 'First Things' ('Det fyrste').
Groop and accompanist Roger Vignoles are well paired, as both like to let the music flow naturally. This puts them in the opposite corner to Anne Sofie von Otter and Bengt Forsberg, whose award-winning Grieg recital (DG) comes with their personalities stamped on every bar.
Where they're in competition (only three songs here), Von Otter and Forsberg are instantly memorable, achieving lift-off with a tremendous sense of elation in 'Hope' ('Et Håb') from the Op 26 set, albeit at the expense of some pullingaround of the tempo from the pianist. There are people who are resistant to the Swedish couple's bold way with Grieg and for them the more traditional approach of Groop and Vignoles will be preferable. The recording quality is first rate.