Actors traditionally wish each other good luck before they go on stage by saying, “Break a leg!”

In the not-too-distant future, they may instead be saying — through a voice simulator — “Blow a fuse!”

Indeed, as leading Japanese dramatist Oriza Hirata recently wondered aloud to this writer, “Will actors at auditions soon be vying for their roles with robots? And are we entering an era in which robot actors will one day take the leads in ‘Romeo and Juliet’?”

Though such musings might seem fanciful, they may soon come true on a stage near you. That’s in part due to Hirata, who is also a professor at the Center for the Study of Communication-Design at Osaka University, and whose “Mori no Oku (In the Heart of a Forest)” will mark the public debut of the Robot-Human Theater (RHT) project he is involved in when it opens in Nagoya on Aug. 21.

That landmark staging follows a demonstration performance of the world’s first robot-human theater two years ago thanks to the combined efforts of RHT’s key players: Hirata himself and two others also in their 40s — Hiroshi Ishiguro from Osaka University, a world authority on intelligent-robot research, and Kazunari Kuroki, president of Osaka-based robot and computer company Eager Co. Ltd.

Back then, on Nov. 25, 2008, history was made with “Hataraku Watashi” (“I, Worker”), a short play specially written by Hirata that was staged for an invited audience in a studio at Osaka University.

Reporting on that possibly epoch- making premiere by the RHT project, Hirata said, “In the last scene, the human actors left and only two robots remained on the stage receiving applause . . . and actually, some people in the audience had shed tears at some of those robots’ lines.

“At that moment,” he continued, while laughing, “I thought that at last I’d beaten Constantin Stanislavski!” (The Russian dramatist [1863-1938] who developed a revolutionary “realistic acting” technique now named after him.)

Hirata was speaking during an open seminar at the Tokyo Performing Arts Market event in March this year. There, he also said, “I proved there that acting can be effected without any inspection of their character’s psychology by the actors, because non-sentient robots were splendidly able to produce an emotional effect on a human audience.”

In fact, Hirata had been fortunate back in 2006 when he took the job at Osaka University. That was because Ishiguro and Kuroki had already planned to create a robot theater there, and so the three of them made a natural team from the outset.

However, what Hirata brought to the project in particular was a determination to create a work of art through robot theater — not a high-tech showpiece to amaze those who saw it without necessarily engaging their emotions.

Meanwhile, at a public dialogue meeting with Hirata held at Osaka University last year, Ishiguro said of his first involvement with play-making, “I thought theater directors would do their work using their actors’ spiritual motivation, but Hirata stated firmly: ‘Actors do not need to have a psychological approach. If they do exactly as I direct, they can express their character’s feelings.’ I agreed with that.

“People often say it seems that my robots have feelings, but of course that’s just make-believe.”

To realize their robotic make-believe, though, was a painstaking process for every human concerned. The rehearsals for the demonstration staging of “Hataraku Watashi” in 2008, for instance, involved Hirata requesting countless changes to the positioning of the two robot actors, changes to the intervals between their lines and requests for their head and arm movements — all of which had to be programmed into their computers.

Once that was done, though, there was no danger that either the male robot (stage name Takeo) or his female counterpart (Momoko) would forget their lines or miss a cue and have to be reminded again by Hirata what to do, in the way many human actors do.

Made by Mitsubishi Heavy Industries with the product name Wakamaru, Takeo and Momoko are both bright yellow and goggle-eyed and stand about a meter high. In “Hataraku Watashi” — as seen on a DVD of that staging — we encounter the robots during just another day in the apartment of the young couple they work for.

However, the husband, Yuji, has lost his motivation to work and just stays at home chatting to the robots and enjoying his favorite meals made by Momoko — while his wife, Ikue, agonizes over what to do about this. Meanwhile, Takeo has also lost interest in working and has become a hikikomori (social recluse) robot. Then finally, with a lovely sunset outside, we see Takeo and Momoko alone on stage at the end of their 20-minute debut performance (their battery life at the time) worrying what’s to become of Yuji and Ikue.

All in all, it was a virtuoso performance by Wakamaru’s finest, who betrayed not a nerve even as researchers and company technicians studied their every move, triggering cameras and taking video continuously.

But as cool as Takeo and Momoko may have been, Hirata reported there was barely a dry eye in the house by the time they took their final bows to loud applause after Momoko had — in an effort to cheer him up — asked Takeo if he’d like to go out and see the sunset.

As to how audience members came to react so emotionally, Hirata somewhat modestly observed that “audiences’ brains make up half a performance’s reality. So, no matter how realistically cast members may act, some people in the audience would feel the work had a reality or not depending on how it is presented.”

In this case, he said at last year’s Osaka University public meeting, he had been able to create realistic scenes and performances by paying minute attention to the word order of the robot actors’ scripts to achieve emphasis despite their flatly monotone voices.

Another crucial factor was that the robots were playing the roles of robots, so removing any audience confusion about their identity that would surely linger if human actors were dressed as robots. This allowed the audience to enjoy the play to the full, including its intriguing and sometimes hilarious dialogue. For example, at one point there is an exchange between Yuji and Takeo that goes:

(Yuji) “How many moons does Jupiter have?” / (Takeo) “There are 39.” / (Yuji) “Why don’t you ask me ‘Why?’ ” / (Takeo) “Pardon?” / (Yuji) “Usually, people would ask ‘Why do you ask me such a question?’ ” / (Takeo) “I see.” / (Yuji) “Got it?” / (Takeo) “Why do you ask me such a question?” / (Yuji) “Well, I just wanted to ask it.’

Scene-stealers, indeed; but Takeo and Momoko, in such exchanges and in the concern they show for the troubled human couple, were not “stealing” humans’ roles — they were acting as robots and the audience was empathizing with them as robots, not substitute humans.

With the success of that demonstration staging behind them, Hirata, Ishiguro and Kuroki are set to present their first RHT public performance — of Hirata’s 2008 play, “Mori no Oku (In the Heart of a Forest)” — at Aichi Triennale 2010 in Nagoya this month.

That play, set in the Democratic Republic of the Congo, was about a group of scientists researching differences between humans and their closest relatives, bonobos, to find out what makes humans human. In this version, though, robots — now with hourlong battery lives — also appear as helpers for the researchers, so allowing Hirata to explore the boundaries between the three “species.”

Just be sure that, if you are lucky enough to see this groundbreaking work, you don’t blow a fuse in your amazement at the end!

“Mori no Oku (In the Heart of a Forest)” — which is subtitled in English — runs from Aug. 21-24 at Aichi Arts Center in Nagoya. For more details, call Aichi Triennale 2010 at (052) 971-6124, or visit aichitriennale.jp/ or www.seinendan.org Nobuko Tanaka’s theater blog (in Japanese) is at thestage.cocolog-nifty.com