Maggie Roche, who has died aged 65, was the eldest of the trio of singing sisters the Roches, whose songs bridged the gap between American folk and pop styles. Maggie brought her low alto voice to the harmonies she wove with her sisters, Terre and Suzzy, in her quirky, often funny but always heartfelt songs.

Maggie received her first big break when she and Terre attended a songwriting course led by Paul Simon at New York University in 1970. The experience gave the two sisters added confidence to write and perform, and when looking for a record company they contacted Simon, who used them as backing singers on his 1973 album There Goes Rhymin’ Simon, paid for their music lessons and then helped produce their duo album, Seductive Reasoning (1975). Though Simon recognised their talent, the experience overwhelmed the two sisters, who disappeared for six months to study martial arts. Upon their return, they were joined by Suzzy, performing as a trio at Gerde’s Folk City and elsewhere in Greenwich Village, New York.

The Roches’ reputation spread: the New York Times identified them as leaders of a new folk revival, and they played support to visiting headline acts. Robert Fripp of King Crimson admired the women’s unusual songs and style, and when both he and they signed for Warner he was ideally placed to produce the trio’s eponymous first album in 1979. The record, which included Maggie’s songs The Married Men and Hammond Song, established their reputation. The follow-up, Nurds (1980), was surpassed by the more acoustic sound on Keep on Doing (1982), which included their unlikely but often requested arrangement of Handel’s Hallelujah Chorus.

Although the Roches never broke through to achieve chart success, they took it in their stride, together writing Big Nuthin’ about a television show that was going to change their careers but which turned out to be a “big nuthin’”. When they played it on Johnny Carson’s TV show, he failed to see the joke. Nevertheless, they paved the way for female singer-songwriters in the 1980s and 90s, with Indigo Girls citing them as an early influence; the Roches guested on a couple of Indigo Girls albums.

Further albums included Another World (1985) and a Christmas record, We Three Kings (1990). Their songs featured on the soundtrack of the film Crossing Delancey (1988), and they provided voiceovers for animated cockroaches in Steven Spielberg’s television cartoon series Tiny Toon Adventures. They toured the UK, appearing at the Cambridge folk festival (1981, 1993) and on BBC’s The Old Grey Whistle Test. They sang on several Loudon Wainwright III albums: he was Suzzy’s partner for a while, and their daughter, Lucy, sang occasionally with the Roches.

Maggie grew up in Park Ridge, New Jersey, in an Irish Catholic family, the daughter of John Roche, an actor, and his wife, Jude (nee Jewell). Her father wrote songs for local political candidates, which were sung by the teenage Maggie and Terre. The sisters caught the songwriting bug, performing at school and church functions. Maggie briefly studied at Bard College, New York state, before meeting Simon.

In addition to singing, Maggie played guitar and keyboards, but she often stayed in the shadows. Suzzy described her as a private person, sensitive and shy, but “smart, wickedly funny and authentic”. Following the 1995 album Can We Go Home Now – for which Maggie wrote the title track in response to their father’s Alzheimer’s disease, and also contributed the song My Winter Coat – the Roches disbanded. Maggie and Suzzy continued as a duo, and a final trio album, Moonswept, was released in 2007.

Maggie is survived by her partner, Michael McCarthy, her son, Edward, and her mother, brother and sisters.

• Margaret Roche, singer and songwriter, born 26 October 1951; died 21 January 2017