Actually, (I had forgotten about this alternate syntax, I'll double-check the docs to make sure it's in there)--you can wrap parenthesis around lines like this:
(NOTE 0 :voice 1 :off 7.5 :dur 0.5 :note 84.0 :marks ((:tremolo 1/4))) (NOTE 0 :voice 1 :off 8.0 :dur 0.5 :note 72.0 :marks ((:tremolo 1/4)))
So if the line starts with an open-parenths, fomus reads everything up to the matching close-parenths and ignores line-breaks--I think this shouldn't be too hard to do from pd...
-David