Critics have been busy providing reasons for you to go see the 20th-anniversary production of David Ives‘ evening of one-act plays, “All in the Timing,” at Primary Stages in New York. (Cast members are pictured.) Here’s another reason that hasn’t, to my knowledge, been reported: The new musical that Ives has been working on with Stephen Sondheim is based on one of those short plays. It’s been known for months that the men have been collaborating on a show that springs indirectly from a moment in an Ives play that caught Sondheim’s fancy. But most of the speculation has been that the Ives work in question is one of his full-length pieces: though no one to my knowledge has seriously thought that it was Ives’ S & M play, “Venus in Fur,” that was being transformed into song, enticing though that possibility may be. (Sondheim is leaving the whips and chains to Roman Polanski, who is working on a movie “Venus.”) Now, the speculation on which playlet is being Sondheimized can concentrate on “All in the Timing.” I doubt it’s the sketch in which the composer Philip Glass buys a loaf of bread to the time-bending, repetitive rhythms of a Glass collaboration with the director Robert Wilson. Nor do I think it’s the bit about Leon Trotsky. An obvious choice is “Words, Words, Words,” which takes off from the premise that three monkeys, left alone in a room with three typewriters, will eventually produce “Hamlet.” But I don’t know for sure. I’ll keep you posted.