Characteristically, musical theater is a spectacle of music, dance and dialogue. From London’s West End to Broadway, popular musicals are typically large-scale crowd-pleasers that make the genre highly commercial. Big productions in the hands of famous musical producers like Stephen Sondheim and Andrew Lloyd Webber can run for years.
Music
Musical theater productions usually include a score, songs with lyrics that advance the plot, and instrumental interludes. The music and songs heighten the dramatic tension within the plot. The emotions or plans of characters are expressed through songs as well as monologues. Some include a "chorus" of characters as a functional device. The choral numbers allow more characters to voice an emotion or point of view at the same time.
Dance Numbers
Dance routines are an integral aspect of musical theater. Choreographed dance or movement adds a physical rhythm to accompany the musical score. A large-scale dance number or two can tell part of the story in an active, visual way.
Plot and Dialogue
Unlike a play, the dialogue in music theater is usually brief and functional. It drives the main narrative forward, but until the final act, the emphasis of the show is on the songs. The plots of older "book" musicals usually dealt with love and romance. In the 1980s and 1990s, musicals also started to deal with contemporary issues such as social, political, rebellion, inequality, peer pressure and crime. Some major hits after 2000, such as "Wicked," "Legally Blonde" and "Litttle House on the Prairie" were based on books, movies or TV shows.
Set and Lighting
After 2000, the top-line Broadway and West End musicals usually had to top each other with spectacular high tech stage sets and lighting. Part of this was due to hydraulics that can automatically create different stage levels, unexpected effects and aid quick set changes. This led to increased costs. According to a 2010 "New York Times" story, the 2011 musical "Spider-Man" cost more than $60 million, and that was before it experienced a run of costly problems in previews. By comparison, "Phantom of the Opera" cost $8 million in 1988, and "Shrek: The Musical" cost $25 million in 2008. On other levels, theater producers with modest budgets, put on musicals with basic sets and non-automated equipment. That's why, even as of 2011, it's far more likely to see those companies staging older book musicals like "Oklahoma!" than any of the tech-heavy shows.