Tom Stoppard is interviewed at the Barnes & Noble Review, where he discusses - among other things - his adaptations of The Seagull and The Cherry Orchard.
JM: You've said about your own plays that the motivating impulse in composition is the next line -- to find out what it is, to be surprised by it, to take what you've done to the next step. In a translation, you know what the next line is. So while there's the consolation of Chekhov having done the heavy lifting, so to speak, is there a fundamental difference for you in the experience of writing when you're working on an adaptation?
TS: That's a good point. You do know what's coming up when you're translating. I suppose the concentration then is on finding a formulation which is speakable and in character -- and economical as well, actually. And in that task perhaps it's actually quite helpful to know what the comeback is going to be, what the next line is going to be. Because you're dealing in rhythms, really. When I'm looking at a speech, parts of it I find immediately -- I think half the time I get there in one. But as to the rest, it seems as if you don't get it in one, you feel you never get it -- you're into your seventh or eighth try, and then you're into your ninth, which you discover to your surprise is the same as your first. It's a strangely maddening process, but essentially an enjoyable one for me, because it's a pleasant challenge each time. It goes wrong if you work too many hours at a stretch. What happens is that some kind of reverb sets in between your natural sense of the language and your translator's brain-load, and you lose touch with some fundamental level of English discourse. Quite often, one might go to bed thinking, "That bit's OK, probably," and the next day it reads much more stilted in some way, because you'd been made un-grounded by the loop between the literal and your own sense of the language.