Low blow! Beloved tenor to sue opera museum over bass-placement!

The fat man sang, and now he’s going to sue.

A battle between a diva-esque tenor and a tiny opera museum hit a new crescendo this week when the former artistic director of the Enrico Caruso Museum of America announced that he would sue the curator of the obscure institution — though he’s not really sure why yet!

The dispute stems from that most operatic of slights: Not only was the tenor Luciano Lamonarca bullied out of his position, but his final performance in his official capacity was tragically undermined when he was replaced at the last minute — by a bass!

Since the museum exists solely to honor the greatest tenor of all time, Lamonarca was enraged by this affront to all things mid-range.

“I’ve done everything for this museum — yet they pushed me out,” said Luciano Lamonarca, the former publicist for the Sheepshead Bay museum. “They wouldn’t pay me, they wouldn’t acknowledge me, and then they took my performance out from under me.”

Now Lamonarca is looking for a way to sue his former employer Aldo Mancusi, who runs the museum out of the attic of his Homecrest home. But their feud didn’t reach a breaking point until that fateful night on April 9, when Lamonarca was scheduled to sing an aria at Borough Hall to recognize 15 years of the museum’s dedication to the late Italian tenor.

Some facts are not in dispute: Lamonarca and his virtuoso pianist were the only performers on the concert ticket that night. Since his hire in December last year, Lamonarca had been complaining that he was never officially named “artistic director” — despite his claims that he did everything in his power to publicize the museum and its Web site — and his desire to turn the position into a paying job.

What he didn’t expect was to be fired — an replaced! — just minutes before his acclaimed recital.

“After the show, people came to me and said, ‘That man’s not a tenor, he’s a bass!’ ” Lamonarca told us. “How could [Mancusi] be so blind?” Or, more appropriately, tone deaf?

This is where the dispute becomes a classic case of he sang, she sang.

Mancusi wouldn’t go into details about Lamonarca’s request to be paid for his volunteer work, but he did deny the most heinous of accusations.

“I have no idea what he’s talking about — it was a world-class tenor,” Mancusi said. “He sang everything he was supposed to sing. We don’t want to affiliate ourselves with people like him — it became a very poisonous atmosphere.”

Regardless, Lamonarca’s taking the war to court. He claims that there was a verbal agreement that he be paid monthly, and that he was fired for writing up a contract.

“I must be recognized for my work!” Lamonarca said. “Until then, I will no longer represent this museum, which I have loved, and been fascinated by, for years.”

Stay tuned for Act II of this tragi-comedy.