They won't smells musty, especially if they have been kept in the freezer. Hop cones are flowers so think about them as flowers rather than fruit which goes bad and stinks. Have you ever smelled old flowers? They smell like dried grass or hay and not much else. Same thing will eventually happen with hops. Before they reach that neutral aroma they can go through a cheesy stage where the hop oils are oxidized. It takes a while, especially in the freezer, to develop those cheesy aromas but even when they start to get cheesy you will still smell some of the hop character. Eventually all the aroma fades and you just get a hay aroma.