This is a stab in the dark, but is it your fav Jonny spielt auf? I can't find a synopsis on line, and Kobbe is downstairs, but there is a composer in the cast.
Accurately stabbed, Don B
Although my advocacy of the piece in the past was a bit of a torch in your darkness
The composer Max is suffering from writer's block, and takes himself on a mountaineering holiday in the alps. By obscure chance he finds a girl at the top of a crevasse whose derring-do has taken her up, but won't get her down again. (By way of thanks she later shags a violinist behind Max's back - but that's sopranos all over for you...
)
There's a snippet of the opera on YouTube, although from Act Two (once they are back in the big city):
http://uk.youtube.com/watch?v=3cwH9V_Ff0E