Voice acting is the art of doing voice-overs or providing voices for animated characters in various works, including feature films, dubbed foreign language films, animated short films, television programs, commercials, radio or audio dramas, comedy, video games, puppet shows, and amusement rides. Performers are called voice actors or actresses, voice artists or simply voice talent. Their roles may also involve singing, although a second voice actor is sometimes cast as the character’s singing voice. Voice artists are also used to record the individual sample fragments played back by a computer in an automated announcement. At its simplest, this is just a short phrase which is played back as necessary, e.g. the Mind the gap announcement introduced by London Underground in 1969. In a more complicated system such as a speaking clock, the voice artist usually doesn’t actually record 1,440 different announcements, one for each minute of the day, or even 60 (one for each minute of the hour), instead the announcement is re-assembled from fragments such as “minutes past” “eighteen” and “p.m.” For example, the word “twelve” can be used for both “Twelve O’Clock” and “Six Twelve.” For some automated applications, such as London Underground’s Mind the gap announcement, the sound of a voice artist may be preferred over synthesized voices because the human voices sound more natural to the listener.