An Upper West Side condo is seeking to force a former “Saturday Night Live” band member from the building — and, no, not for playing jazz too loud.

An explosive new lawsuit details a frightening late-night outburst in May by the veteran musician — one allegedly so severe that board members are seeking to force him out, The Post has learned. 

Lawrence Feldman, 75, an accomplished alto saxophonist, has owned apartment 3C at the Admaston condominium on West 89th Street since 1986, when records show he purchased the unit for $146,500 — about $450,000 today. Similar apartments in the building now trade for between roughly $1.6 million and $4 million, records show.

The 251 Condominium’s board filed suit in Manhattan Supreme Court this month, accusing Feldman of violating building rules and creating what it describes as a dangerous nuisance for residents and staff. The complaint seeks a permanent injunction and asks the court to require Feldman to sell his apartment.

However, a family member claims it was a one-time occurrence stemming from an epidural gone wrong.

According to court filings obtained by The Post, the dispute stems from a series of incidents that allegedly unfolded on May 14 and May 15.

The building’s management company claims in court documents that Feldman “went on a violent, drug fueled rampage, threatening to kill two people.” 

The filing claims he attempted to enter a neighbor’s apartment, pursued the resident manager to his home, struck a building employee and was ultimately removed from the property by police in handcuffs.

One doorman, Rasim Paljevic, told the court that Feldman spent hours roaming through the lobby area, where he was “sometimes muttering and sometimes screaming.” 

Paljevic said in docs Feldman repeatedly shouted … “F–k [the board president].” The doorman further alleged that he witnessed Feldman “smack” a porter during the confrontation. Paljevic wrote that he was “scared” and had “never had something like this happen in all of my years working in buildings.”

A second doorman, Smail Ramusevic, described another confrontation hours later. Ramusevic told the court that Feldman was “yelling and screaming” and complained that a neighbor owed him money. 

According to the filing, Feldman called the woman “a b—ch and said he would kill her.” Ramusevic also alleged that Feldman threatened him directly, saying “He said he would kill me,” before grabbing him by the thigh.

The most serious allegations come from neighbor Bridget Gilbertson, also known by her married name Bridget Russo, who lives across the hall from Feldman.

Gilbertson told the court she was asleep and home alone while her husband, Christopher Russo, was out of town, when around 2 a.m. a loud pounding erupted outside her apartment door.

“I heard defendant outside my door screaming and menacing: ‘Bridget Russo. F–k you. You c—nt. I am going to kill you, Bridget Russo,’” she wrote. She further alleged that Feldman yelled, ‘I’m going to f–k your brains out Bridget Russo.’” Gilbertson said she immediately checked that her door was locked and called 911.

She later described seeing Feldman in the lobby after police arrived.

“He was laying on the floor repeatedly screaming ‘F–k you’ to a police officer,” Gilbertson alleges. She claims he kicked furniture, said he had a knife and continued directing vulgar remarks toward her, including “Look at me you f–king scared b—ch.”

Gilbertson said she and her husband have since left their apartment and are “living out of a suitcase in a hotel,” because they no longer feel safe returning home.

Resident manager Almir Feratovic, who lives in the building’s basement apartment with his wife and three children, told the court that he had never experienced anything similar in more than two decades working in residential buildings.

Feratovic added that he also received reports that Feldman had been telling staff members, “I am going to kill Almir.”

The condominium’s attorney, who declined The Post’s requests for comment, argued in documents that residents and employees remain fearful because Feldman returned to the building the next day after police took him to the hospital that night. Court filings state that staff members who claim they were assaulted or threatened continue to encounter him while working, while neighbors say they remain concerned for their safety.

Feldman’s wife, Sandra Lee Church, disputed the broader characterization of the dispute.

“I was actually asleep when this happened,” Church told The Post.

Church said the controversy stems from a long-running conflict with Gilbertson.

“Well, our neighbor … we have many, many years of not being on good terms with her, not terrible terms, but she’s very difficult,” Church said. “And in this incident, I just don’t think that Lawrence was in his right mind. He was worried about an epidural that had effects on him.”

Church maintained that “it was no one else in the building that had a problem with them” and said the issues centered on the dispute with the neighbor. She added this was an isolated incident.

Feldman did not return The Post’s request for comment. Gilbertson declined to comment. And Russo, Gilbertson’s husband, declined to comment. 

The legal fight stands in stark contrast to Feldman’s long career in music.

According to his professional biography, Feldman has recorded and toured with artists including Frank Sinatra, Tony Bennett, Barbra Streisand, Rod Stewart, Linda Ronstadt, Liza Minnelli and Steely Dan. He was a member of both the “Saturday Night Live Band” and The National Jazz Ensemble, performed with the New York Philharmonic and has played on hundreds of recordings, film scores and Broadway productions.