If you had been standing outside apartment 12E in the white brick apartment building at West 22nd Street and Ninth Avenue in Chelsea on Thursday evening, you would have heard songs taking you back four decades, to a time when it almost seemed that by singing loudly enough, it might be possible to stop a war.

It is on Thursday evenings that Henrietta Yurchenco, a 90-year-old former City College professor and radio producer, collects a few of her students to sing the same protest songs she sang and taught 40 years ago. The war on their minds is a new one, but many of the songs they sing, like The Banks Are Made of Marble, Where Have All the Flowers Gone? and Study War No More, were the product of wars long past. 

Ms. Yurchenco, who this evening was wearing a jewel-studded peace symbol around her neck, still believes in the beauty and power of folk music. And her former students, now in their 40s and 50s, find that same beauty and power in their teacher. 

Ms. Yurchenco taught ethnomusicology at City College in the 1960s and ’70s, when another war divided the nation. She held singalongs then, and in 2005, she revived the tradition with friends and former students.

Her charges group themselves around the kitchen table, surrounded by trailing ivy and colorful animal sculptures from Mexico and Guatemala, two countries where she has traveled and recorded traditional music. Ms. Yurchenco runs the singalong like a seminar: distributing lyric sheets, commenting on the repertoire, fielding questions. Every evening has a theme. This evening, the theme was labor, and the lineup included such songs as “Dark as a Dungeon,” Merle Travis’s song about the perils of coal mining, and “The Banks Are Made of Marble,” popularized by Pete Seeger.

When Ms. Yurchenco taught courses on folk music and the blues, students flocked to her home for singalongs. She barely had enough space for everyone. These days, perhaps half a dozen singers show up, although other musicians drop in. Among the regulars is Bob Malenky, a self-described “red-diaper baby” raised on such labor movement staples as “Joe Hill” and “Union Maid.” 

At this singalong, after a rendition of “Join the C.I.O.,” Ms. Yurchenco described a fight she had with the song’s author, Aunt Molly Jackson, a cantankerous, Kentucky-born labor activist and folksinger. The fight took place during a picnic in the 1940s at Bear Mountain State Park, attended by musical luminaries like Leadbelly, Woody Guthrie and Mr. Seeger. “She was a peppery dame,” Ms. Yurchenco said of Ms. Jackson. “You had to watch out for her.”

Although Ms. Yurchenco’s folk repertoire is vast, she prefers songs that couple easy tunes with provocative lyrics. “We don’t do any mediocre songs,” she said. “The melodies are good; the words are wonderful.”