When people think of opera, they usually associate it with Pavarotti or Domingo or Callas (or pick your favorite). They also tend to associate opera with Puccini, Verdi, Wagner or Mozart. As they should!
However many opera singers not only sing opera, but oratorio and art song as well. Oratorio is opera based on a biblical text that is not staged. Good examples of this are Handel's Messiah, or Mendelssohn's Elijah.
Art song or Lied (meaning song in German), or Mélodie (in French) is a more intimate form of Western Classical singing. It involves a pianist and a singer (or occasionally a small string ensemble). Typically the performing venue is much smaller than an opera house (ranging from 50 - 1000 seats). This music focuses on the text and the interplay between the singer and the piano. There are no elephants, zebras, giraffes or costumes.
There are many well known composers that wrote hundreds of art songs based on poetry from little known poets to the heavy weights such as Heinrich Heine, Victor Hugo and even Shakespeare.
My favorite art song composers are Schubert, Schumann, Fauré, Vaughan Williams, Finzi, Duparc...and the list goes on.
This type of intimate art form is not performed as often in North America as in Europe. If you have a chance to experience it, do so! They are a quick fix for the music bug (1-1.5 hours max).
Here's a great example of this increasingly rare art form (written by Robert Schumann with poetry by Joseph von Eichendorff):
