Here is text on Nords website about the Felt Piano:M1tsos wrote: Its possible to be the same mellow instrument with different micing or eq etc or difference distance of recording the mics etc..
"...a medium sized upright piano fitted with felt between the hammers and strings to provide a soft, warm and delicate piano sound."
They didn't disclose the make and model of the upright piano, so It may be one of the medium size uprights they've sampled in the past. They physically inserted felt to change the sound; they 'prepared' the piano in addition to whatever microphone placement or EQ they used.
I think it sounds very nice and could be effectively used for soft romantic pieces, film soundtracks, acoustic accompaniment for vocals, small ensemble works and so on.