The online catalogue of the Alexander Turnbull Library in Wellington provides further details:
Lydia Williams is in the centre, playing the banjo. Seated at the right is her sister, Amy Devereux. The man with the camera is Russell Duncan. The other man’s identity is unknown but it is possible he was a member of a group such as the Fisk Jubilee Singers, a troupe of Negro singers and musicians who toured New Zealand in the late 1880s. Photograph taken by Lydia’s husband William Williams.
Russell Duncan was later to become a well known photographer and historian of Napier.
Another photo by Williams, below, also from the Alexander Turnbull Library, seems to show the same group, on the same day.
What junipers are these, inlaid
With flame of the pomegranate tree?
The god of gardens must have made
This still unrumored place for thee
To rest from immortality,
And dream within the splendid shade
Some more elusive symphony
Than orchestra has ever played.
— Grace Hazard Conkling, from “Symphony of a Mexican Garden“