Before the start of every cruise, a muster drill is conducted. During these drills, the general alarm sounds, and all crew members and passengers are required to report to their muster stations. Once all passengers have reached their stations, crew members explain and demonstrate various emergency procedures (how to put on a lifejacket, what to do if the ship must be abandoned). Cruise ships also conduct many crew-only emergency drills, including specific drills for the ships’ firefighting teams.
From what I’ve gathered, in case of a fire that threatens the safety of the ship’s occupants (due to a risk of smoke inhalation, for instance), the captain may sound the general emergency alarm, requiring everyone to report to their assigned muster station while crew members try to get the fire/smoke under control. Most muster stations are located on the lifeboat deck (right by the lifeboats); however, certain muster stations can be located inside the ship (in the main theatre or in a certain lounge, for instance).
The video below shows what it’s like when the general alarm sounds during a real fire. The ship in this video appears to use a mix of sounders, strobes, and a tone being broadcast over the public address speakers. I’m not sure what’s going on with the alarm signal in this video, however, since it’s supposed to consist of seven short blasts followed by one long blast (the tones don’t seem to be properly synchronized in this case). Note that the person filming is mistaken by saying that this alarm is for “abandon ship”; this is the general alarm signal, simply requiring people to report to their muster stations.
The next video shows what it’s like when passengers make their way to their muster stations. In this video, the general alarm signal can also be heard (bells and public address system). The man yelling “1, 3 and 5 that way!” at 0:33 is referring to the muster stations. In this case, it appears that the uploader’s muster station was located in the ship’s theatre. The crew can be seen preparing the lifeboats for launching, but I don’t believe the boats ended up being necessary in this case.
Should a complete evacuation of the ship be required (extremely rare) due to the severity of the situation, the captain would sound the “abandon ship” signal, which consists of a single long blast on the ship’s alarm signals and horn. The passengers and crew would already be at their muster stations at this point and they would now start to board the lifeboats. https://www.youtube.com/watch?v=N_ZWyE6QZl0 This is what the alarm signal would sound like and https://www.youtube.com/watch?v=cVDTfke6VxE this is what the evacuation would look like (footage from a crew-only drill).
I’m far from being an expert on these procedures, so if I’ve made a mistake in this post, please feel free to correct it! This information is based solely on what I’ve gathered from going on a few cruises and participating in muster drills. I have no idea how these emergency procedures would work on other types of ships. Also, none of the videos posted above belong to me.