When watching the map when in an alliance. You can access the radial wheel to select the speaking trumpet. When looking at the map with it selected you can speak to all the ships in the alliance. The sound comes from a strange cursed skeleton skull placed on the shelf.

The sound is not as loud as if someone was using the speaking trumpet. More like someone talking on a walkie talkie trying to get contact with the alliance ships.

This could be handy when in need of assistance if attacked by other ships. Or when the alliance need to move to an area for a event etc.

The cursed skull (speaker) could be an event in itself to get. And something everyone get's at a later date like with the drums and speaking trumpet etc....

What do you think?

Edit: When communicating with the alliance the skull's jaw could move and the curse make the hollow eye sockets glow as the old evil magic activates. There could also be a skull up on deck by the ship's wheel. So that you can hear what's going on with the alliance. But you would have to go down to the map to communicate back.