“Improvisational theater” always means comedy.  There doesn’t seem to exist any improvisational tragedy/drama.  Why?  I don’t think its because improvised drama would not be as interesting or entertaining as improvised comedy.

  1. Its just selection.  People become comedians because they are funny in real life.  To be funny in real life you have to know how to create humor out of the random events that happen around you.  People become dramatic actors if they are good at understanding and reflecting dramatic themes in text.
  2. Its just training.  Improvisation is what you practice if you want to do comedy.  Its not a useful skill for dramatic actors (absent an already existing market for improvising tragedians.)
  3. Improvisation is by its nature funny.  Seeing something you don’t expect is usually going to be funny even if it is nominally tragic.  Like slipping on a banana peel.  So improvised tragedy is just a contradiction in terms.
  4. To make drama work the players must have a high degree of coordination in terms of the development of the story and that is too hard to achieve through improvisation.  By contrast, absurd plotlines add to the comedic effect of improvisation.
  5. Improvised drama would indeed be no worse than improvised comedy but that’s not the relevant comparison.  It would be much worse than scripted drama.  In other words drama has a larger range of quality than comedy and to hit the highs you need a script.
  6. Improvisation inevitably breaks the fourth wall.  The audience is wondering “can they do it?” and the actors are self-consciously playing on that tension.  Breaking the fourth wall tends to heighten comedy but cheapen drama.

(Plundered from a conversation I had with Chris Romeo.)