Trying to play a accordion song I heard, doesn't sound right

I heard this song on Youtube

Grainne’s Grace (Lullaby)

I think it is in the key of D but it sounds high.
Any suggestions?
Would a low D harmonica work better?

Hey Brian - yes I just tried playing along with my Low D Lee Oskar and it worked. Only problem was having to do the -3’’ which is a little bit tough. I was able to do it. It would be so much easier though in a “Paddy Richter” tuning, but I checked Brendan Powers website and it looks like Low F is the lowest harp they sell in that tuning, unfortunately.

Alas, you’ll just have to do the -3". The rest of the tune is easy to play though, and sounds great on the Low D.