I discovered this image recently while reading about piano. I discovered this young Portuguese pianist photo, Vianna da Motta, while learning in his early stages. I assume this is some kind of keyboard instrument but its not clear and the format is very unusual. Which instrument is it?
Just found this picture, it's the same picture from the original question by nsn, but with a framing and caption from a magazine. The legend says "Vianna da Motta aged five, playing the harmonium flute". I believe it's precisely the same instrument model shown on the photo posted by alephzero, to the details of the turned shapes of the legs.
The specific name seems to be related with a french origin and making of the instrument. Quoting from Harmoniflûte wikipedia page (my translation from french):
"The parisien factory of Constant Busson...built mainly accordeons ...and other instruments. Constant Busson decided to explore the market of instruments betwwen the accordeon and the pump organ, ... and invented the harmoniflûte, presenteng it at the 1855 Paris World Fair. Another harmoniflûte was invented by Mayer in Paris at roughly the same time".
It looks like one of pump organs, like:
The instrument was invented in 1855, and da Motta was born 1868, so this was the high technology of its day, not some boring old pianoforte!
Harmoniflute, a kind of reed organ with only two ranks of reeds, both 8', but the second is celeste-tuned i.e. When played with the first rank the second produces a regular beating, due the tuning diference.