Not totally a call to muster, but we were awakened at 3 am one night at sea. In my sleep-filled stupor I recognized the "7 short 1 long" blast, and knew it was not a drill. I knew I needed to get up and put on some clothes, and wait in my room for further directions. After about 15 minutes, there was a ship-wide announcement that a fire in the engine room had triggered the alarm, but all was under control and the fire was out.