Mountain Dulcimer vs Hammered Dulcimer Music

I have been playing the mountain dulcimer for a relatively short time and just learned of a hammered dulcimer group that meets in my area. I have been invited to partcipate but they only use hammered dulcimer music so I would be on my own to figure out how to play along with them. I have played in other jam sessions where HD's were part of the group, so I know it can be done. However, I don't know enough about HD music to know what I need to do to play along with them. Any suggestions would be much appreciated.

Thanks.

Wanda