St. Vincent worries how her incarcerated father is coping in prison every single day.
In 2010, the rocker's stockbroker father was jailed for fraud, receiving a 12-year sentence.
Speaking with Britain's Q magazine in a new interview, St. Vincent, real name Annie Clark, confessed she rarely speaks to her dad, chatting with him on the phone around once a month.
"I'm not amazing at answering the phone in general," she said. "But he talks to my siblings more often. It's definitely a mourning. It's mourning a loss but in a specific way."
According to Q editors, the Digital Witness singer thinks about her father every single day, and fears for him due to her dim view of the U.S. prison system.
"There's so many facets to that pain, or tragedy, if you will. Even under the best circumstances, prison is a horrible, unnatural place, and in America, there are so many rungs lower you can go," the 35-year-old explained, adding that her interest in penal reform goes beyond her concerns for her father.
"America is in the deepest need of prison reform, and I would think that even independent of my dad. The amount which we disproportionately incarcerate people of colour in this country, poor people, increasingly women, and the fact that, like all things in America, it's also privatised and incentivised, it's deeply corrupt."
In an interview with The New Yorker magazine earlier this year (17), St. Vincent confessed that her 2011 album Strange Mercy was about her dad being jailed.
Fans have speculated the star's latest album Masseducation also references her personal life, as her ex-girlfriend, Cara Delevingne appears on the record, and it contains a passionate ballad titled New York.