Carl Wilhelm Soderstrom writes:
 > > WTF is a compose key?  
 > 
 > look at an honest-to-God DEC VT dumbterm, and you'll see a 'compose' key on
 > it. other dumbterms probably have them as well.
 > As Mr. Goldman implies, it's used for composing foreign characters like the
 > Spanish characters that have the ~ over them, and such like.

Apparently Suns have these.  I gave away my Sun 2 a while ago (I hope
it's found a happy home), so I can't verify this.