Alice Ripley in ‘Next to Normal’: knowing when to leave

The money — and the media — behind Broadway serve up the illusion that hit shows are frozen on opening night.

Whatever superlatives were showered on “Billy Elliott” or “In the Heights” when they opened years ago are still screaming at us from posters in the lobby and on little signs dangling on the marquees.

With Broadway being such a huge business — and tourist magnet — it has always puzzled me that shows aren’t revisited on a regular basis by critics (or arts consumer reporters) to see if they are still delivering the goods.

Lip service is given to the notion of theater being an art form in which every performance is — and should be — unique, but few talk about the problems that arise when a play or musical runs for months or years. Actors in a hit certainly remain “artists” but they are also cogs in a commercial machine.

The truth is that a long-running show almost always has its ups and downs in terms of what an audience experiences.

Some performers have the physical equipment and the dedication to maintain a role for months and months (I saw William Daniels in “1776” almost two years into his run and he was still a fantastic John Adams).

Others get bored and go on auto-pilot.

Some stars do weird things to keep themselves interested (i.e. theater history accounts of Barbra Streisand in her second year of “Funny Girl,” and Zero Mostel in his second month of “Fiddler on the Roof”).

Then, there is the case of unusually strenuous roles that can wreck performers, perhaps because they were not designed to be played eight times a week for an extended period of time.

Which brings me to Alice Ripley and her Tony Award-winning performance in the psychodrama musical “Next to Normal,” which has been running since the spring of 2009.

I didn’t catch up with the show and Ripley until yesterday’s matinee and my first thought after the show was that it is a very good thing the actress is leaving the production on July 18.

I’ve been a fan of Ripley’s since I saw her breakthrough performance as one of the conjoined twins in “Side Show” in 1998, but it was painful to listen to the sound of her singing voice in “Next to Normal” Sunday.

Yes, some of the rock-tinged score is meant to sound harsh — the show is about a suburban wife and mother who has been breaking down mentally for 16 years — but Ripley was the only performer on stage whose voice was such a strangled rasp that half of the words she sang couldn’t be understood.

The sound engineers appeared to be playing tricks with her track in order to pump up the sound, but it only emphasized the vocal problems and in some scenes made Ripley’s voice seem to be disembodied (because it was so loud and clearly not coming from the direction of the woman on stage).

Maybe the actress had laryngitis. Maybe she had a bad cold. But in either case, she was not the doing the audience or herself any favors by performing.